What i conclude is that the more expensive their feed the better they are, as in more adaptable in most situations, but also more complicated and difficult to raise, not to mention most likely to have screwed stats.
Lif before evolution will make you cry because it has such low attack power, meaning it'll have a really hard time leveling up. On a side note i noticed that Mental Sensing only need intimacy to learn, so if you really want it to be easy, don't train it at all or stop at level 9 with nothing learnt, leaving it with 3 skill point. Feed it until it evolves and have the skill unlocked, immediately master Mental Sensing. That way it'll have more power, provide it has sufficient SP to use it.
Same goes for Amistr, you can use the same method but it'll be weaker than Lif when it comes to offence even with the attack boost. It's main job is defend after all.
Vanilmirth and Filir however don't need to evolve to train up easily. The difference is the burst damage skill they already have, one on ranged magic, one on melee attack. Evolution only gives them stats boost and a new I'll-hate-you-with-passion-after-this but destructive skills.
Like WG said, Lif should most likely to be suitable in WoE. Then again, most situation actually. Amistr is most suitable for mob gathering before YOU(or your plants) finish them with AD(with the Defence and Adamantium Skin, it'll be really hard), it's not built to kill effectively. Vanilmirth for brewing and 1-on-1 PvM(preferably low MDEF), probably PvP too. Filir for killing magicians only, also 1-on-1 PvM(preferably low DEF).
Yes, it does. I'd tested it myself since i brew and apparently switch homuns until i feel comfortable with my current Giga Pudding, which greatly improves brewing but very weak.