some thoughts based on my limited understanding.
need to consider the yearly budget costs as well with any deciesion.
some thoughts
onprem : hardware cost - one off - add 6 year life cycle
hardware support and maintence / extra disks / disaster recovery / backups
upgradeability i/e adding additional storage how easy this is could be.
security - server updates including firmware/bios + hypervisor and OS updates
say 20k every 5-6 years
+ UPS's
more to manage and maintain.
Wireguard Client (alternative to direct access) + VPN alt Backup.
Time investment and maintanablity + Documentation + team size supporting + plan if you leave (may not be your problem then but who ever takes over will need information on set up).
Technical Knowledge needed / have
tied to physicall access, may need at least two internet lines on differant circutes to try and add redundence (additional costs) speed tbc i.e. BT / Virgin Media - what coffee shops are near by and do you like the coffee?
Depends if home working isnt mandatory i.e. staff can get to office if they need to, to access files.
Windows / Linux knowlege
Cloud : your at the mercy of the cloud providers and the rates they charge. E3 would be looking at maybe £10.5k a year (based on Office E3 £22 per person per year for 40 people)
but they offer a range of usfull services and you dont need to worry about storage growth, just costs.
i'd suggest the E5 licence i think.
as per Zefan Data egress costs ! often overlooked
and plan and costs to move off platform if needed in future.
Assuming no issues with Internet providers or Azure then you should be fine (has happened)
less to manage in theory
there is the hybrid approach.
something like
https://bluexp.netapp.com/blog/talon-fast-works-with-cloud-volumes-ontap-to-unify-data
this ones a bit more tricky.
i'd suggest sharepoint as that also includes onedrive and a host of office integration and sharing options. but everything from MS at moment to me seems like a Beta, but thats probably the ring we are on in office.
the cross working of multiple people on a document is very usefull for things like spread sheets. but only if you have the budget for it and prepared to pay for it regularly and staff are sensible ish with what they are doing.
personlly i can never really see how cloud long term is very feasable when compared to local on-prem.
you'd need to work out your requirements a bit more i feel, and get some costs from an MS representative to see if you can get a good deal.
