Indeed, needs can be quite specific
There's some providers who specifically market VPN circumvention protocols (either proprietary or based on non-standard ports, or both, or both and more!) but don't offer some other useful features.
I was previously a VyprVPN customer - currently I'm both currently a Nord and TorGuard customer for one specific reason: Nord don't provide any portforwarding facilities and have no plans to despite previously saying it was forthcoming. You can torrent (and fast) through Nord, and as long as you want to only use public trackers with DHT and Peer Exchange, you'll be fine - seeding on (and in some cases, downloading from) private trackers is impossible. TorGuard's port forwarding is a bit fiddly to set up but works.
Protocols-wise, Nord, VyprVPN, PIA, TorGuard, ExpressVPN, AirVPN etc offer broadly the same feature set.
Directly comparing Nord and TorGuard, there's some differences:
1/
NordVPN offers SOCKS proxy and VPN as part of one subscription; TorGuard sells VPN and proxy products separately. You can buy them as a bundle for 40% off, or buy each individually with a 50% off code and save a bit more, and it becomes the same price as the 3-year-for-$99 NordVPN offer at that point (mad but true).
Nord offers OpenVPN, IKEv2/IPSec, SOCKS5, and CyberSEC DNS adblocking/privacy stuff. They discontinued L2TP and PPTP on December 1st 2018 to the displeasure of a fair few users!
TorGuard offers OpenVPN, L2TP/IPSec, PPTP and OpenConnect (an open version of Cisco AnyConnect - which they dub their 'Stealth' VPN product).
Both providers have guides on their site for setting up the protocols on different devices. Nord's looks bit slicker but fundamentally all the info is there for both.
2/
Nord appear to have more servers in a few key countries (US, UK, Germany etc). TorGuard seems slightly biased towards US customers given the add-on features and "gigabit premium network" which, for an extra cost, gives faster backbone access for superfast broadband - but only on US servers. Nord is open about their server lists and server naming. Some categories of servers are for different purposes - P2P, Tor, double-proxy etc.
TorGuard have a list on their 'Network' page showing server clusters by country for their main protocols, however server IPs are hidden behind DNS load balancing. If you want to find a specific server and manually use that as a 'custom' server - which is required for port forwarding - prepare to do a couple of dozen rounds of speed tests with multiple reconnects inbetween finding new unique server IPs. I've only managed to find one UK server so far after 30+ tests which gives me over 300 mbit/sec upstream, the downstream is always much slower than NordVPN (pretty much guarantee any UK server peered to IX North will give me >400 mbit/sec).
Latency is good on both networks. I don't bother to disconnect when gaming. TorGuard actually shouts about their VPN network decreasing overall latency in some cases due to how they've peered. That may be so but I've not thoroughly tested.
3/
Peering and physical VPN server locations are noteworthy. I'm on a very fast connection, easily capable of maxing out these VPN servers, so it's interesting to see how speeds differ. I suspect Tor have fewer unique servers (in the UK at least) which are more loaded than Nord. If not that, Nord are perhaps better at more efficiently implementing aspects of the VPN server side - or they just buy more powerful servers/pay for better peering/have fewer UK customers/are using voodoo.
I have noticed that they have lots of servers in Manchester and the North of England as well as London, which is great as my ISP's peering is
lots better to LINX Manchester than it is London.
Nord appear to be a big M247 customer; TorGuard are a big UK2 customer.
4/
NordVPN have some clever reverse-proxying and DNS techniques going on, transparent to their users - but means you can use a few key territory Netflixes, iPlayer etc (via certain groups of servers which they list in their knowledgebase) without any other tweaks. TorGuard specifically do not offer this unless you pay extra each month for a residential IP, which considerably bumps up the price.
5/
Nord Android app is slicker than TorGuard. TorGuard desktop app has some useful functionality but it's a bit more crudely designed, however there's plenty of customisation and flexibility regarding port selection, protocol choice and even encryption level right within the app. (caveat: some of their OpenVPN configuration is reportedly a bit borked, see their forums for further discussion on crypto negotiation...)
Nord desktop app is now very noob-friendly but you can still use older version as long as you don't mind dismissing the upgrade nag screen. (VyprVPN's Android app was also quite slick but the service was a little slow overall for me when I was a customer (2017-18).)
6/
Nord, as TorGuard, and most of the big providers, support PPTP, OpenVPN, L2TP and other protocols which means should you wish to VPN at a router level, most router firmwares which ship with a VPN client baked in should work fine. I've had success with AsusWRT-Merlin running on NordVPN previously, not got that router set up on the new connection yet however so haven't tested TorGuard, however it should be identical process to use on that. Certainly offer the ports, protocols and even have an .ovpn generator on their site. (Nord's ovpn files and certificate key pairs are buried in documentation links, and some were moderately hard to find). Had weird problems with a few UK NordVPN servers totally refusing to handshake on OpenVPN for no apparent reason, even support weren't sure why.
7/
Support from both TorGuard and Nord has been pretty good. TorGuard prefer ticketing system; Nord do email. Response times and helpfulness about equal.
8/
Nord have apparently demonstrated (via pwc audit, and a couple of test court cases) that they're zero log. Company registered in Panama but they operate out of Cyprus I think. TorGuard proclaim to be similarly strict zero logging but they of course store customer info, as will Nord. You can pay through PayPal and avoid a fraud check (as PayPal will do it) - or pay by crypto and it's not done as you don't have to share any info.
https://thebestvpn.com/118-vpns-logging-policy/ has a list of over 100 VPN providers and their policies, compiled last March, I don't think much has changed.
I think it's most important to judiciously trial any VPN provider, and read beyond the usual crop of 'VPN recommendation sites', many of which make bank from referrals and paid promos. Read user forums, track performance over time as related by customers, etc. Do trials of several at once if practical, where the providers offer a trial period, as you might find one provider gives you stunning performance with your ISP and others fall short.
I wouldn't rush to join PIA, I've read reports of contention and poor configuration recently from user forums. However, of course, user forums are mostly full of complainers
and I've never tried PIA myself.
Feel free to hit me up if you have any other queries, and there's bound to be loads of customers of various providers on here...
NB some VPN companies are just whitelabelled resellers - e.g.
Ghost Path who are a SlickVPN reseller, and their customer service and network performance is apparently not stellar.