this is for my first build which im hoping for it to last for a good run, (dont mind upgrading parts like processor). I know that amd is the cheaper one but the processor is pretty underpowered compared to the intel which with every review i have seen is better. Is it worth paying the extra price for the intel if i can easily upgrade to i5. or is the amd fx enough, but considering its low power per core.
What im looking to be able to do with the build is light video editing, using 3d rendering programs like cinema 4 design without a large waiting time, some light gaming like minecraft, but then standard games too like battlefield.
In general the i3 2120 wins over the FX 4100.
When overclocked the FX 4100 can equal the i3 2100 in some applications/games.
The only issue is that the FX 4100 when overclocked uses a lot more energy than the i3 2120. This makes it a loser in my book.
The FX 4100 is beaten by even cheaper CPUs from Intel like the G series Pentium Sandy Bridge chips that were featured in this months' Tom's system builder marathon $500 machine. http://www.tomshardware.com/reviews/gaming-pc-overclock...
I'd look at a Z77 chipset like the one you have chosen and get a Pentium G series since you plan on upgrading the CPU in the future.
Check out the i5 3570K in the $1000 SBM machine from today. It is a killer setup. http://www.tomshardware.com/reviews/build-a-pc-overcloc...
The gist of it is that the FX-4100 and the i3-2100 (ever so slightly slower than your i3-2120) are basically neck-and-neck on gaming when paired with anything less than a 6950. The Intel platform offers more gaming versatility along the upgrade path (even stepping up to the top-of-the-line FX chip isn't going to net you any gaming performance gains), but AMD gives you cheaper and easier access to higher core counts for rendering and video editing.
Either setup will play Battlefield on high at 1080p with acceptable framerates, so if that's all you're looking for, I'd go with AMD since stepping up to 8 cores will only run you $180 (honestly, if you can swing the extra $70-ish over the 4100, I'd just start out with that). With Intel, you're looking at around double that for a hyperthreaded quad core, and well over $600 for a hex core (including a new motherboard).