I've always preferred intel and may opt for an i7. However AMD is much cheaper.
How does an Am3+ like the phenom x3 compare to the i7?
nobody knows because nobody has ever used it.
amd still tries to make processors?
I use AMD processors, but I don't know how they compare to Intel's and I frankly don't do anything particularly demanding with them
I believe the FX series is newer and more powerful than Phenom and probably more easily comparable to the i-series too. They both use AM3+
"If you're only looking for gaming, X3 should be sufficient. You can buy X4 940 if you want to keep the rig for abou 2~3 years. If you want maximum performance, Core i7 is the way to go, but its also the most expensive (by far)."
http://www.tomshardware.com/forum/258524-28-phenom-phenom
It looks like i7 out preforms them, AMD processors should be fine.