@techlord
General rule of thumb, those that spout mostly negative, off topic stuff in a thread like this arent worth listening to and are only in it to try to cause troubles (sad gits, but such is life). Im sure even someone new though can see the genuine responses vs. those trying to instigate trouble (you watch, those same people will now try to justify themselves on the back of me mentioning this (although Ive only said this to stop them doing thier usual nonsense)

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In regards to the actual questions it depends on what you want to do with it. If you want to play old amiga games and whatnot then AROS may actually be something worth trying as its version of uae is orders of magnitude times faster than that for os4 or mos. Having said that though, if youre content to use windows, then winuae is pretty much the ultimate amiga emulator.
Personally I'd probably try that 1st, learn the system, find what software you like and what you feel is missing. After that perhaps try out AROS (which runs on standard pc hardware and is free/open source, so its not gonna cost you a penny) and see if a dedicated "amiga" system is for you. It is the rawest of the NG Amiga derived systems, but should give you a feel for whether an amiga based system is for you, at which point you could then go on to spend more money if you want mos or os4 (or stick with aros if you enjoy it). While it (AROS) is the rawest of the 3, it does have some of it own advantages. Cheap, most powerful hardware by a long shot (only amiga derived system to be able to play 1080p video for example), best hardware support, best 3d subsystem (you watch a few particular mos people claim that its unstable now though (which is a crock, most of the negativity comes from those that dont like the fact other options are superior in some ways)) and the fact its x86 means that there's often codepaths in software that make the end product far faster (uae and dosbox come to mind).
This isnt to say AROS is the best choice, that's all down to the individual, but for someone not wanting to invest much money while they get a feel for the amiga it's a good place to look. The main reason Ive elaborated is becuase unfortunately this community is for the most part insecure and there's a lot of people that will stick up for thier system of choice and badmouth others even when its not warranted. I just thought Id give you the true lowdown on AROS before one of a few usual suspects twist and contort th truth for thier own fragile egos. They probably still will, but at least now youve been warned and will know what to, and not to listen to.