The 3 are very evenly matched. People saying the Shadow Hawk loses 90% of the time are just wrong. The Wolverine has a large SRM launcher, but actually has less missiles it can fire (the SRM-6 only gets 90 missiles vs the SRM-2's 100). Against the Griffin, get in close. Against the Wolverine, stay at 6-7 hexes if you can and keep your TMM high.
Against the Wolvie, you basically want him taking shots with his SRM at about 9s. You're gonna run him out of ammo. If he needs an 11 or something, he won't fire. You want him to be tempted enough that he shoots, but still misses most of the time.
The 3 mechs perform different roles. The Griffin gives highly mobile fire support. The Wolverine is designed to mix it up with other mechs of its weight class. The Shadow Hawk is a jack of all trades. It can carry inferno missiles, specialist AC ammo, smoke LRMs, etc. It also hits basically every range band, so it's good for shooting at multiple targets. Park a SH in heavy woods on a hill, and fire the LRMs and AC at one target, the medium laser and SRM at another.