Need help choosing between these two comps (no givaways here.)

For your question:

iBuypower is better due to higher processor cache, upgradeable ram size and usb 3.0
sata 2 vs sata 3 is negligible in hard drives.

Anyways, where do you live? you don't need to "build your own" parts, you can "pick your own" parts and let the computer technician on that place assemble it for a fee, ofc not from best buy :P

Neither for gaming... those are more designed for media.

AMD 8 core isn't ideal for gaming purposes, most of the time it's just idling/wasting those cores and bottlenecks in other areas. It's best for use in multi-tasking / high end applications.

Intel has 2nd Generation (Sandy Bridge), 3rd Gen (Ivy Bridge), and 4th Gen (Haswell) PCs which also redesigned the motherboard to work with the CPU. CPU now gets direct access to memory and graphics processing, therefore less bottlenecks, therefore 60-80% performance increase over 1st Gen PCs.

Recommend getting a i5 CPU (non-k) such as the Ivy Bridge-based Core i5-3570 (3rd Gen) or Haswell Core i5-4570 (4th Gen).

i7 CPUs also include hyper-threading, but isn't really needed for gaming. The K versions of the CPU are unlocked for overclocking purposes, however this is now just a waste of money as you won't ever need to overclock!

Then your motherboard should support this, make sure the socket matches, for example i5-3570 (3rd Gen) has a Socket LGA1155 (it will be labeled on both). Recommend getting a gaming motherboard from the ASUS ROG (Republic of Gamers) series, Gigabyte G1 Sniper series, or similar. These have much better layout and design quality.

NVIDIA GeForce GTX 650 graphics isn't meant for gaming purposes, rather application and media. Sure it can play some games, but was not designed with that in mind. Suggest GTX 660Ti or better / GTX 760 or better, for high quality gaming.

Your PSU should be ideally around 600-750 Watt and be 80 PLUS Gold certified -> to be stable, allow for future upgrades and having quality rails.

Your Memory optimal levels for gaming are actually at DDR3 1600MHz CL7 or CL9 timing. 4GB if your Operating System is 32bit or use 8GB if using 64bit. Slower tends to bottleneck, but faster won't show more than a 1% performance increase towards gaming.

I would actually advice buying individual parts compared to getting a pre-made. That way, you can easily replace the broken parts as opposed to having to replace the whole computer if the motherboard or PSU breaks.

Make your own.

The iBuyPower is the better choice. While those 8 cores may seem wasted, it just means an upgrade won't be necessary for a very, very long time. I have A8-5600K 3.6ghz Quad in my comp and it makes an amazing difference in gaming. While some people say Intel is better, AMD offers the same performance at a lower price. If you're on a budget, go with AMD. Save up a couple hundred bucks and you could grab yourself a nice GTX 660 or Radeon 7870. Both are amazing graphics cards and run every game I've seen flawlessly. (Radeon can use the PhysX drivers btw). Bottom line though, go for the iBuypower.

Neither, build one for yourself instead. Could probably do better at around the same price tag unless you REALLY want that flashy case.

However since you can't, even though I don't see why not. I'd personally say the one with the Zambezi, I use an FX-8150 myself, I love it.

Both of them are decent, but overpriced if you ask me. From the two of them, i'd go for the 1st one.