AMD Phenom II X4 975 V.S. Intel i3 2100

Well, they are kind a similar at performance(i3 may be a little bit better), but Phenom have more room for overclocking.
But really Wei is even considerable score to check out performance?

i3 - Try getting the 2120.

The i3 performs about the same if not better than the 975. The i3 would be a smarter buy since you can upgrade to Ivy Bridge later on while the AM3+ socket is dead.

WEI means nothing.

Click the following review which compares the AMD Phenom II X4 980 vs. the Intel Core i3-2120 which should give you and idea of the performance in games.

http://www.techpowerup.com/reviews/AMD/Phenom_II_X4_980...

i3.

The i3 is a dual-core CPU with hyper-threading, the AMD CPU is a quad-core. However, the AMD CPU is older tech and has had its day...still a good CPU, but there are better choices. As has been said above, the i3 would allow you to have an open upgrade path...currently, all the way to the i7-2700K, and if the rumours on Ivybridge are correct it'll also support S1155 so you'll be set for those CPUs also.

It would help if you told us what your intended usage was.