You're probably going to get a lot of 'opinions' on this one....... I'm going to agree with Joanna - depends on the horse.
I have a Paso Fino and a TWH. Between the two....I'd say my paso is smoother. BUT - I haven't actually had my TWH in his RW for any length of time to actually be able to 'compare' (he's been naughty and trotting!)
Recently, however - my paso has taken to trotting as well (I'm sure he learn it from my TWH!
) So NEITHER of my horses is 'smooth'! But.....we're working on that!