All Samsung i9000 Galaxy S phones run Architecture version ARMv7-A with a core of Cortex-A8. It is the same type that the Apple iPhone, touch, and iPad use. Samsung's CPU is called "Samsung-Intrinsity S5PC110". Apple iPad/iPhone4G uses the Apple A4 CPU which uses the same architecture and core as well.
Now the HTC EVO 4G with Snapdragon uses something different.
It uses a Architecture version ARMv7-A with a core of Cortex-A9 MPCore. This is what Nvidia Tegra2 uses as well. Devices using Nvidia Tegra2 are the Zune, KIN One, KIN Two, etc... http://en.wikipedia.org/wiki/Nvidia_Tegra#Tegra_250
You can find out all this information with some research guys. I got most of it from Wikipedia. http://en.wikipedia.org/wiki/ARM_architecture
And if you wanna know a fun little fact, Samsung was the first CPU ever put into an iPhone. Samsung is a lot more reliable than HTC in my opinion, so buying the Epic is not a bad decision at all.
Lets not forget that the RAM count for a lot as well. Both phones have a 1GHz CPU. But both phones have different RAM/ROM.
The HTC EVO has a RAM capacity of 512MiB and ROM Capacity of 1024MiB. The Epic has both 512MiB.
Now lets go into the GPU's on the phones.
The Samsung Epic 4G uses the PowerVR SGX540. That is the same "type
" of GPU used in Dreamcast, It is also the same "type
" of GPU that the Apple iPad and iPhone 4 use. However, they use the SGX535. Even the Palm Pre and Palm Pixi use PowerVR. http://en.wikipedia.org/wiki/PowerVR
And just for clarification. It is only called "Hummingbird" because it mixes PowerVR SGX540 with Cortex-A8. Samsung pretty much takes the chips and develops their own like any other company.
As for the HTC EVO 4G. It uses Adreno 200. Which was previously "ATI Imageon". So it is an AMD/ATI GPU inside of the EVO. This is usually found in phones only. The Nexus One has it, HTC Desire, Incredible, and Droid Incredible have it. Even the Dell Streak uses one. But they are all different versions. The Droid Incredible and HTC EVO 4G both use QSD8650, while the Nexus One and Dell Streak use QSD8250.
And for another clarification. It is called "Snapdragon" because it mixes Adreno200 with Cortex-A9 MPCore. And like I said before, it is how companies make stuff.
Its like a computer, you buy certain parts that are good. But on those parts, there are other parts that might be good or bad that you have to look into.
Now the question is. Do you want a phone that uses a chip that was once inside the infamous Sega Dreamcast years ago with a QWERTY keyboard and TouchWiz 3.0? Or a phone that uses a phone standards and tries to sell their product by adding a Kickstand and a 8MP camera?
That is how you find out exactly what you are buying.
I know I am buying the Epic due to its QWERTY, Hummingbird, Super AmoLED, Touchwiz 3.0, 4G, as well as many other features that I am too lazy to name off lol.
And Yes I did bring Apple into an Android discussion lol. The only reason why Apple phones are so fast is due to their OS being so dull. Now we just wait for the Hummingbird 2 to come out and hope to god Samsung gets it first so the iPhone can definitely get screwed and have to make a new OS instead of making like 1000 versions of 1 product.
PowerVR SGX544XT + Cortex-A9 MPCore = Superbird! lol...