I don't have an Intel i7 CPU (just a laptop) and I still use FSX 'just because' it's the only flight sim I've used after moving from Microsoft's Train sim which dates back 9 or so years ago.
A lot of people will say "well, it depends"
If you want max frames and have a slow/fast computer than go FS9. There are still a number of developing groups making aircraft for this including Pairbus and Skyspirit (breakoff from FSPro[?]) and really in general you'll find older and more experienced simmers, and there are many ways to upgrade the visual appearance in FS9 to get close to FSX.
If frames won't bother you too much and you won't mind a...younger community then go FSX. Likewise, different freeware/payware groups and developing for FS9 and different free/payware groups are developing for both FS9 and FSX (hint) and different free/payware groups are developing only for FSX or moving toward it, as lots of newcomers mostly want the latest sim especially with all the stronger computers coming out now. Drawback is the numerous problems you will find at first but there are always people to help (in the right places), but many people who use FS9 will look down on you (in some cases stereotypically).
Heck, I'm only 16 but not all the "young 'uns" and "FSX noobs" and "kids with big pcs" a lot of the people in the FS community see us as are bad eggs by heart. I know I'm speaking as someone who uses FSX but ultimately it comes down to your own situation with hardware/patience.
Of course, MS Flight doesn't seem
that far away but still needs more information before I can think of switching over to that but also
since I've only been simming on FSX (or any FS for that matter) for just over a year.
A lot of people will probably find problems with my post but the people that would help most are people who have extensively used both instead of one-sided information from either, but hopefully there is
something worthwhile to you in my post

!