Im using coil its a serta i got it online cost me 75$
I spent $230 on a foam 2 sided mattress. I went with foam because it's light so it will be nice and easy to pull up and take sheets off, and the 2 sided is one for babies which is really hard and water proof, then you flip out it for the softer side when they're toddlers. The coil mattresses are a lot heavier but last longer. I went to buy buy baby and spoke to a sales guy, he was very helpful