G5s are the best for video editing -- way faster.
I can do basic editing on my powerbook (G4, 1ghz, 728mb ram), and it works fast for simple things in imovie. Good for home movies and hobbiest movies.
For heavey-duty editing get a G5 system (dual is good) with Final Cut Pro. That'd be the best for quality movies. It'd also encode fast, and render quickly. It's the best system that you can get for home, but it does cost more than the G4, but less than other movie-making systems and works great too.
the newer Starwars movies, I believe, were made on a mac, using final cut pro.
But for home/hobbie movies, G4 is good. Have 64 mb video ram, with regular ram, too. Although, I have 728mb, I've never used it all. Not ever. I ran activity monitor once while rendering an affect demo in imovie -- the processer was at 100%, but i was only using 500mb ram, maybe a bit more. but not all of it.
The speed of your processor is important, cause that's where the calulations take place. The faster the processor, the faster the rendering and encoding.
For example, what takes 5 hours to render on a G4, it'll take 1 or fewer hours on a G5 (found that on a site, when someone was talking about handbreak and encoding dvd movies two hours long into avi...or something that. Dual G5, was taking half an hour...compared to five).
It really depends on what you what, and how much you're willing to spend. How often do you edit movies -- are you going professional? Professionals should go for G5 with final cut -- you wont find a better system for that price.
A dual G5 in US dollars is going ot cost you $3000 plus. And then you'll need a display, get 17" cinema or higher. The colors are better on a mac, and more standard. Windows uses funky colors, and I find darker ones too. You can set the color standards on a mac, too.
There is a reason why so many producers in hollywood have a mac. there's a reason why so many people in the media use macs too. They work well, they are reliable, and you can get a system that really kicks but -- and $3000 isn't a bad price for a dual G5, for making movies that you're going to sell.
Final cut pro is about $1000 US dollars.
For home stuff, G4 works good. I'm using a powerbook G4, 1ghz, and it works fine for the stuff that I do. And I don't do a lot of video editing, just simple home stuff here and here. Nothing complex. I'm more into writing, cause that's what I do.
check out apples site on video production:
http://www.apple.com/finalcutpro/
Also, if you're doing professional movies, you'll have to move beyond the home camcorder. A good digital video recorder will cost you lots -- above $5000, 10,000 would be a better one to choose...a home dv camcorder costs $300-$600. You'll need to invest in some other equipment, like lighting, a LCR meter, etc.
it totaly depends on what you're doing.
BTW, final cut works on a G4, and does a bit more than imovie, so that'd be middle ground. You can get something called final cut express, which is cheaper, but has less power than pro.
--nate