As you spec in Beast Craft your pet (wolf) will increase in strength. The pets available at 32, 40 and 50 BC spec all have combat styles and occasionally proc disease. Before level 32 your pet will do nothing except interrupt your target, do pathetic damage, and die quickly. I strongly suggest speccing 32+ beast craft; having a snaring pet with a little muscle adds loads of utility to hunters, and if you want to engage multiple targets you need that pet. 32, 33, 40 ,41, are your best spec options. 50 BC is rarely worth the cost; 32 is the sweet spot.
I ran the 32, 40, and 50 pets against the crush mob on pend. I have calculated the percentage that each pet performed the various procs available to it. I ran them all in the side position so that all the procs would be available, and it seems they really did make the pet a lot smarter in the way it chooses its styles: pincer (side style) was the most common style that appeared in all 3 cases. I ran the 32 pet with the lvl 33 pet buff, and the 40 and 50 pets with the level 41 pet buff. This test does not show damage increase between the pets – just proc rates. The damage increase is nice (though costly), especially on the classic servers.
Percentages (rounded to the nearest decimal):
Pet Level: 32 40 50
Garrote: 2.7% 4.4% 10.5%
Pincer: 7% 10.4% 15.6%
Achilles' Heel: 0.5% 0.7% 2.4%
Disease: 4.9% 5.2% 5.7%
Misses: 41.6% 36.9% 26.4%
NOTE: there is a possible error in the disease results. I collected these numbers by counting key words from the log, and I've been told that there is no log created if the pet casts disease when the target is already diseased. I can't remember if I calculated the disease number from the "<target> is diseased" message or not, and I haven't had the time or inclination to look into it further. All the other number on this page are accurate.
Numbers:
Hunter's Avatar:
Attacks: 587
Garrote: 16
Pincer: 41
Achilles Heal: 3
Disease: 29
Misses: 244
Hunter's Elder Protector:
Attacks: 597
Garrote: 26
Pincer: 62
Achilles Heel: 4
Disease: 31
Misses: 220
Hunter's Elder Avatar:
Attacks: 614
Garrote: 64
Pincer: 96
Achilles Heel: 15
Disease: 35
Misses: 162
The level 40 and 50 pets have an ability called frenzy. Once every 30 seconds (10 seconds after initial cast) you say frenzy (/macro frenzy /say frenzy) and for the next 10 seconds your pet will attack at an increased rate. It is also more vulnerable to attack during this time.