I'm an avid FSX user, but I've now got lots of XP10 hours under my belt.
FSX is great, but it can still take more money to get it as good as you see on these screenshots. (Active Sky Next, REX Textures, ORBX scenery, UK2000/et al 3rd party airports and of course the payware planes). You don't want to invest in that and then find that you'll have to buy those licences again for 64 bit P3D.
The XP11 news is exciting and I'm waiting for the official release of the product before downloading my purchased copy. And the great thing is that you'll get free updates for the life of the '11' product; which for £60 is amazing. I cite the P3D 2.5 users that were charged again for the 3.x upgrade (which could have been 2.6,2.7 etc).
ORBX have now released news of their support for XP10/11. PMDG are on board with their DC-6 and rumours of bringing their 737NG to the platform. The IXEG 737 Classic is awesome, but has so far lacked updates included an FMS 'Hold' functionality.
However, when FSX is under a tenner on Steam (DoveTail's bugfixes apparently make the product run better than the DVD version), then you can't go wrong.
As for the 64 bit issue. XP10 is 64 bit (and 32 bit). FSX is 32 bit which means it has a smidgen less than 4 GB of memory to play with. Which sounds loads, but with all the addons mentioned above, you'll quickly be 'flying' on the edge of out of memory exceptions.
And unfortunately, all the above works best of an SSD, so that would be another purchase.
This hobby does't come cheap.