Of those three seats, my son and nephew think the Triumph is the most comfortable....and it definitely works better for sleeping for them.
The Apex is decent, as in it has the high weight limit and tall top slots and converts to a decent booster...but it lacks EPS foam and it's tough to unbuckle the harness.
The FPSVD is nice seat, it just seems to be a little less comfy than the Triumph (but the cover washes up better/easier!).
If I were picking b/t the Apex and the Triumph, I'd go with the Triumph almost every time (unless the child was really, really close to outgrowing the harness and would be going into a booster very soon).
hths
henrietta