I only use characters I've taken an interest in. Most of the top tiers are interesting to play. If you look at the Stier alone you have 7 completely different and unique playstyles.
At the lower ends, only like one or two method of attack they have seem effective. For yoshi, eggs and SH Bair are really the only methods of approach that are fairly safe. With Snake I can mortar slide them, grenade them, ftilt them, grab and jab them with relative safety.
So to me, higher tier just show a lot more variety in the game play than lower tiers. Of course, Falco is pretty stale when I think about it at times, but it doesn't bug me. I have a growing interest in using peach even though I don't know what options to use for a particular situation half the time xD