Liepard's usable special movepool can be counted with just a hand (Dark Pulse, Hyper Voice, Hidden Power/Hyper Beam if you really want to stretch it). Not really a good thing imo. It's worth noting that Liepard is slightly faster/stronger than Raticate, but Raticate has a better STAB move (Return vs. Night Slash) and has things like priority, Guts, etc. It is possible to use SD Raticate to some effect, sure it won't be as good as say, Minccino killing everything with Tail Slap, but it is a plus for Raticate. Also 64/50/50 bulk isn't anything better than 55/60/70 bulk and Raticate can actually do stuff like SD/Guts, which Liepard lacks access to. In the end, the only thing that Liepard really gets is availability (seriously if it can do anything between it and Rattata this would be something) and a slightly higher speed stat, which isn't very significant for in-game purposes. Having priority attacks is also a plus for Raticate as it allows it to do some decent damage while outrunning, and you also need to note that Watchog and Herdier lack priority.