I really don't have a good answer for that, but I can tell you that all the companies are the same as far as email support goes. If it's a simple answer, they'll reply with the info, if it's not you may either get a canned responce about something nothing related to your problem or they just won't reply at all.
I'll tell you one of my experiences with my own equipment. A few years ago I purchased the Brother MFC-9100C. (I know I know, I actually bought a MFC.) but anyway, one of my first tasks was to scan images directly into PSP 6 (This was before 7.0 came out) The images would come in, but only in Greyscale. If I used their software, I'd get it in Full Color. So I emailed them about the problem, which they emailed me the fix. Which was simply I needed to add a line in one of the twain INI files to include the support for Paint Shop Pro.
However, somewhat recently I had to contact them again reguarding why the darn things makes the system unusable when printing. When I originally bought it, I thought it was just because I had it on an old 233MMX system, and it really required something a bit more powerful. So for the most part I used the old system as a print server, just so it didn't bog me down on my system. But when I upgraded my system and made the print server an AMD 950MHZ, I expected better performance out of the MFC. So I emailed them to see if there was something I could do about it. I figured they answered me the first time, they probably will again. Well, that was almost a year ago now, and I still haven't heard from them. I did figure out the problem though. It's a Brother. That's the problem.

Seriously, I knew Lexmark was bad for that, but until the MFC I hadn't had too much experience with Brother directly. But I have recently found out that all Brother products bog down the system, no matter what the system configuration is. UGH. I guess I'll stick with HP next time.
For now I'll just leave it on the print server, and I'll run just fine.
As for email support vs phone support. I can't really tell you what the difference is other than how it is perceived on the other end. But I can tell you, that the only real way a problem can be resolved is by picking up the phone and call. Granted, you sometimes have to pay LD charges, or they'll charge for the support, but in either case it's more likely to end in solution than email.
I would just like to stress one more time, that ALL the companies are the same in this reguard.
Take Care,
RJ