I've got an Amiga 1000 with 1Mb of RAM and I've also got an expanded A500 so I'm able to tell you exactly how it is. An NTSC A1000 will not be able to play PAL games or demos and this is a major drawback since about 60% of the best ECS games and about 95% of the best ECS demos are PAL. Also, some games that run fine on the A500 will have strange graphics corruptions or just fail on the A1000.
The colour composite output is a major bonus in the A1000 and so is the nice solid design (and A1000 "nostalgia factor") but I don't think these are enough to offset the lack of PAL support, compatibility, built-in-ROM or available expansions.
I can also now admit that I spent way too much on expanding my A500 when it would have been much cheaper and better for me to just buy an A1200. In fact, even though I've upgraded and configured my A500 as far as it can possibly go, I'm still planning on buying an A1200 so that I can go further.
If you're just planning on playing games, use WinUAE. If you're planning on having an upgraded Amiga with harddrive to play games with WHDload (which is waaay better than WinUAE), then get an A500 or A600. If you want to do even more, get an A1200. The A1200 is the cheapest and the best solution.