wet food or dry food? mine both

Loki is a mixed dog, 2.8 year old, and she is a bit picky. Dry food every morning and wet food at night, I mix a spoon of wet into the dry so the smell is strong enough for her. Vet said the wet food is good for the water intake, since Bangkok is so hot and she drinks less. But the wet food is more expensive and leaves more mess. So I keep it to 3 or 4 times a week, the rest is dry. If you change food, do it slowly over 7 days. Loki had a bad tummy when I switched too fast last year.