I don't think there is a best assembler - I guess whatever you can get, that you're happy with, and within your pricerange is the best.
Personally I use Devpac. I got it off a coverdisk back in the day, as did a few of my friends. We started learning together, so it was convenient.
I tried a couple of others, but by then I was familiar and comfortable with Devpac. When I decided to buy - I bought Devpac 3. No other reasons really - it was what I was, and still am comfortable with on the Amiga.
I think the days of assembler/language snobbery are well behind us at this point. Most coders have left for other pastimes or greener pastures. Anyone wanting to start something new, in assembly, C, E, Blitz, even Amos is to be commended and supported as far as I'm concerned.
Shop around, hunt around, try things out, and choose what gives you a pleasant experience.
