To elaborate one what Yupply said about crit rating:
Lightning Breath does more damage than Gore. Both ravagers and WSs can learn Bite.
Lightning breath: 99 to 113 nature damage, with chance to crit.
Gore: 37 to 61 damage (74 to 122 when double damage procs). Single damage or Double damage can crit.
So it's pretty easy to see that Lightning breath is going to do more consistent damage. It has a 100% chance to do about 100 damage (assuming that it lands. Both LB and Gore have a ridiculously high miss rate). Gore has a 50% chance to do 37~61 and a 50% chance to do 74~122 damage. Gore's crits have the potential to be bigger, but it won't happen as often.
So... Why not take a wind serpent right away? Well, since it does less base damage than a ravager, the hunter needs enough crit to proc GFtT enough that Lightning breath can be spammed often enough to overcome that base DPS gap.
A lot of hunters won't take a Windserpent until they're up to 40% crit, but that's pretty easy in T5+ gear with raid buffs. Honestly, though the difference isn't significant enough that I would discourage using a Windserpent before 35% crit. If you like the way that wind serpents look (or you'd rather have a pet that eats fish), then by all means, take one!
And another nifty thing is that they eat Manna Biscuits!
Edited, May 30th 2008 5:18am by ProjectMidnight