70-200 f2.8 IS + 2x tele converter...but which one?

Hey guys
im thinking of trying a 2x teleconverter for my mark 1 70-200 f2.8 IS. I've seen kenko, vivitar, bower,digital concepts, canon, sigma, etc. Is there anything the Canon 2x converter does better than the others? Are they pretty much all the same? I realize it'll be 5.6 all the way through, and slower AF, but the few dollars spent is definitely less than the 100-400 ($1300 roughly used) and for not using it THAT often I couldn't justify spending the money.

if anyone has any experience in any of these brands i'd appreciate your input before I waste any more money! thanks!

I think all Canon ones should work for your MK1 lens, but so should all the third party ones. I think the MKII and MKIII versions of the Canon are weather sealed.

The only real benefit to third parties is they may be less expensive and they may work with lenses the Canon ones would not. (Canon ones will not work with third party lenses nor with non high end Canon telephoto lenses)

have you tried 'other' brands on a 70-200 f2.8?

if you can wait, the 2X mkIII will hopefully be superior quality. if you can't wait, i'm sure many people will be dumping the mkII to buy the mkIII, so the used prices should drop.

I have the 2X Canon Mark II on that lens and it works fine.

If I had a 2.8 I'd go for a Canon 2X for IQ reasons.I have the tamron because it is non reporting which gives me AF in good light with my 300 f4.One of my next purchases will be a Canon 1.4 to see if I get
better IQ.

I have a Canon 2x TC that I use on my 300 2.8. I did have a Kenko, but it was somewhat "cheap" overall, and I found the IQ to be better with the Canon TC. I have both 2x and 1.4x, and am pleased with their performance on my 100-400 and the 300 2.8. I've always heard the Canon TC's are made with "L" quality glass, and the IQ of the shots I get seems to agree. Over the past years, I've pretty much stayed away from third-party optics. Pretty much guaranteed that a lens costing 20% of a Canon lens won't deliver the same quality. Yes, I'm a Canon booster (unpaid, of course), but having so many lenses and TC's over the years has taught me an expensive lesson. Better to spend too much than not get enough for what you spent!