I have ridden in both the 45 Yacht and the Regal 4460. (My father-in-law owns the latter).
We sea trialed the 45 in St. Pete last year and my father-in-law put a deposit on it and the dealer mucked-up the deal; so, he bought the Regal instead.
My observations, (and my wife agrees), the Formula is better on fit & finish hands down. The Regal, ( we spent 4 days on over Labor Day), was a difficult cockpit to manuever about with only four on board! Too many levels to negotiate after a day in the sun and 2 or 6 adult libations
The hardtop supports seem to get in the way everywhere you look. Cockpit layout/design definitely goes to Formula.
As far as cabin...I'll have to say, when I was deciding on what to buy, there seemed to be a simplistic approach to Formula's cabin layout. But, after owning my '07 31PC for a while and then being aboard other boats, several of which have been Regals and BayRays, I mean SeaLiners, I mean Sea Rays...I now know what I like so much about the Formula design! It is the simplistic, clean and efficient design that makes me "feel" as though I have more room than others in my class.
I think, at least for me, the Formula approach to their cabins is like a fine scotch. It's an aquired taste...some just never get it.