The regular X-7 is basically an A-5 with a slightly better cyclone feed in a bigger milsim body. The TM-15 is an Invert Mini in a milsim body. The TM-15, because it is based on a high end marker, will offer better performance, though it may be a little more complex and require a bit more care. That's not to say it isn't reliable, just that regular maintenance (i.e. cleaning) should be done more often and will require a bit more work.
The TM-15 requires compressed air. And you will need to buy a loader to keep up with the marker. The X-7 runs on CO2 or compressed air and the hopper (cyclone) is included.
If you really want the best performance, the TM-15 is the way to go. However, for ease of maintenance, ability to use CO2, and lower price, the X-7 is the way to go. You pick what is important to you.
Another thing to consider is the X-7 allows a great flexibility of looks. It can be an M4, G36, MP5, UMP, etc. You have tons of bolt-on accessory variety in stocks, mags, sights/carry handles and whatnot. The TM-15 is more limited to the M4/M468/SCAR look.
The X-7 Phenom though, should be on par in performance with the TM-15. It is designed like a high end marker. It's still too early to really tell how well it will do though. It looks like it may give the TM-15 a run for it's money.
If you have to decide right now, I'd go with the TM-15. It's been out for a while, the performance is established. How well the Phenom performs in the long run isn't known. It's not even for sale yet (just pre-orders).
I think it would be best if you wait a little bit until some preliminary tests come in on the Phenom. Then make your decision from there. But I really don't think you can go wrong with the TM-15 either way.
EDIT: For some TM-15 info, watch this vid: http://www.youtube.c...h?v=AAPdY511dm0
My friends on Team FEAR did a pretty nice overview of the features and performance. They have a ton of vids on many different markers, so check a few others out if you have the time.
This post has been edited by Jackson: 23 October 2009 - 01:49 PM