What are the pros and cons of each?

420ez is cheaper. 420ex supports ETTL, which the ez does not. That's the main difference.

check out http://photonotes.org/articles/eos-flash/

I would get the 420EX which works with the TTL - I have this flash and it's excellent. I have the 400XTi - but used it with my Rebel 2K and 350XT.

Liz

What are the pros and cons of each?

Thanks for the help, i just have one more question to ask then. I see the EX is better but I wouldnt be using it much on my rebel xt. Should I go with a 220ex/380ex? or an earlier version?

I have the 430EX; I wanted the 550 but price was a problem! However, for what it is worth, great flashes! I would suggest go for the best you can afford - better range, good performer!