I'm trying to train pets and was wondering which was better for pet XP: feeding a pet a snack they love (say, an Onyx Shenlong [] getting the Bogwich[]), or feeding them a Mega Snack (the same pet getting Mystic Dragon Fruit [])?
A "loved" snack will give the pet 2 extra points above whatever the base level of that snack. So, if it's 25 points, then your pet "loving" it makes the total 27. A mega snack starts at 25 points and can currently go up to 55 points. Many of the better ones offer 30-50 points. Obviously, 40 or 50 points is way more than 27. So I'd say that most mega snacks are going to give you more training bang for the buck, especially when compared to a much lower ranked "loved" snack.
Sometimes, though, we can get lucky. For example, Deer Knight pets "love" Captain Cantaloupe, which also happens to be a mega snack worth 45 points.
Something else to keep in mind is that the talents our pet will learn as we level them up are set at hatch. Feeding them different things won't change the talent, it only helps to fill the stat bars (which can be filled with any snack giving the relevant XP). Feeding a pet snacks they love will not make them more likely to heal us, or more likely to get more desirable talents...it literally only means they gain 2 extra XP from the snack (+1 if they 'like' the snack).
On my first wizard I spent an eternity training my beloved siren on loved snacks instead of my biggest snacks because I thought she would love me more hahaha...nope, it just took longer and she still got terrible talents (that I was noob enough I appreciated anyway because she was my baby!).
Always go for the biggest snacks you have - they default to the first page you see when we are about to feed our pet, with the biggest to the left. The only time to go for slightly smaller ones is when your biggest won't fill up the stat bars that affect the percentages for talents. Then go for something that gives the right type of XP to fill the bar but also has high overall XP to level your pet quickly