The honest answer on hot weather, since everybody wants to hear that they can have both.
Ventilated gloves are a compromise and they should be chosen as one. Mesh where the leather would be is less material in the places that matter. A good summer glove keeps the palm and the outer edge fully covered and vents the back of the hand and between the fingers, which is where most of the cooling comes from anyway and where least protection is needed.
A glove that is mesh across the palm is not a hot weather compromise, it is a bad glove.
So the buying rule for summer: vent the back, never the palm. Perforated leather is a good middle option - it breathes noticeably better than solid leather and keeps the abrasion resistance.
On the waterproof pair: waterproof membranes make gloves bulkier and less tactile, and the cheap ones are usually protective in name only. If you ride in rain regularly, it is worth having a proper pair; if it is occasional, over-gloves that go on top of your good gloves are a cheaper and better answer.
Two pairs covers almost everyone: a proper summer glove and a proper winter or all-season one. Three mediocre pairs is the arrangement most people drift into, and it is worse than two good ones.