Forgive me but I'm a bit of a guitar newbie when it comes to this stuff. First off, which one is better and why? Also, they both claim to simulate different amp/cab setups. Are these any good? And if they simulate all sorts of amps, then what amp do I run it through? Sorry if this is a stupid question, but I need advice and help.

Here are links to descriptions of the multi-effects pedals:

Both are good pedals but still don't make up for having the real thing. Pedal performance is really dependent on the type of amp you have, what situation you're using it in (live or studio) what kind of cabinet you have (if applicable) etc.

Generally those pedals are designed to be run through a nice clean signal on a nice clean amp. If you are looking to get one of these tell us what gear you have now, what genres you play and budget. Like I said your amp will play a HUGE role in whether they sound good or not.
Well I like to play metal and rock type stuff. I really don't have a budget but I don't want to spend thousands of dollars. What kind of amps (brand names would be helpful) would make these sound good and what might be a good amp that I wouldn't even need pedals like these for. Would stacks or combos be better? What are the advantages of having these pedals if I could just have an amp where I wouldn't need them?
Well if you don't have a specific budget and by the sounds of it you don't have an amp yet, I would suggest a Peavey 6505+, Splawn Nitro or a Marshall JCM900. Any of those amps won't need a pedal for distortion and you can get individual effects as you need them. They can also be paired with a seperate cabinet if you go for a head. This will be more expensive than getting the pedal and a cheap tube amp but will be much better in the long run.

I suggest because you're a beginner though getting a Peavey Classic 30 with a few stompboxes (individual effects). This will be a much more versatile setup IMO

As you get better and develop an ear for tone you will outgrow multifx very quickly
I have a POD PRO and a ZOOM 2020 I prefer the POD but to tell you the truth get a good amp with effects and thats all you really need I use the effects built into my amp more than i use the prosesers