Why? I understand mastodons but why leopards?
Leopards are quite good, at least on paper, as well. They are among the few pets with 2 additional, 3 total attacks, only smilodons get more. However leopards compared to smilodons:
- get better AC, eventually by a good few points,
- can trip enemies with main attack which is always nice as it can provide with AoOs for everyone within reach,
- after a few levels they should be using DEX for both attack and damage rolls (I think). And of curse DEX is also AC. This is handy when you want to buff them,
- and finally they end as medium sized instead of large. If you use several pets in addition to some characters on the frontline it might be a plus. Supposedly it can get too crowded while using several large pets in some situations.
However smilodons still get 4 additional attacks instead of "only" 2 and can't be beaten in terms of raw damage output so I wouldn't say that they are "noob choice". They're THE choice if raw damage potential is what you are looking for in a pet. If you want more AC and want the pet to contribute something to the party other than their own damage then leopard becomes very good. Personally I'd probably diversify if I had more than 1 pet in party. 1 smilodon + 1 leopard for example. But that's just me, not some objective truth. I'd like some diversity in my zoo.