Would you prefer adjustable straps for your baby?

I crochet baby clothes, but not being a mother myself I don't really know what is ideal. So, the mothers of babies out there, would you prefer straps that were adjustable (tie or buttons?) or straps that were sewn on and couldn't be moved? Also, for a diaper cover/bloomers, would you prefer an elastic waistband or a drawstring-type waistband? Thanks for your help!