well, i'll try and compare ivy/lucas.
i think that ivysaur definitely has a more effective aerial deterrent in bair than anything lucas has.
while on the ground, both characters are fairly similar. for spacing, lucas ftilt is similar to ivy ftilt and dtilt. lucas jab is faster than anything ivy has, but has poor range.
punishment wise, ivysaur has bullet seed as a very quick and painful punisher up close. lucas on the other hand, has jab/ftilt/dtilt. otherwise, both characters' fsmashes and usmashes are similar in terms of start up and kill power.
razor leaf is more spammable than pk fire. razor leaf has more uses than pk fire (both approach and retreat/space). razor leaf can be reflected but will only hit ivysaur when he's close enough to use a different option, usually bair into follow up, but also a dash grab. at that same range, lucas only has pk fire and perhaps a dash grab, afaik. additionally, i'm fairly certain that moves like bair/ftilt/dtilt/jab will cancel a reflected leaf anyway.
just a few things i wanted to put on the table.
edit for levitas
i agree, debating this is boring.
however, ivysaur CAN follow up a razor leaf, because unlike lucas, ivy can di forward as he uses it. at closer ranges, it becomes much more difficult for lucas to reflect the leaf. this is why razor leaf is a nice tool for ivy to use as an approach, not just to force an approach from the opponent. finally, leaf has less ending lag, although it isn't a huge difference.
why would someone be shielding at 1.5 times the range of pk fire? O_o lol. if i see the pk freeze coming, i'll try to get in lucas's face as quickly as possible, or just air dodge/sidestep/roll from the freeze. shield is an option but why let your shield diminish by taking the attack when you can easily avoid it otherwise?
you mention that lucas doesn't want to follow pk fire up...but if that's true, then how are you going to follow up a pk freeze into shield?
sure pk freeze is pretty safe for lucas...but again, how often will you hit with it?
charizard's glide sucks hardcore lol. chaos can tell you how most of the guys here laugh at his glide and glide attack lol. usually glide is just used in place of midair jumps. glide attack has poor range. basically glide isn't very useful in any matchup, but particularly against lucas because of pk freeze. regardless, zard doesn't lose much, if anything at all, by not gliding.