For whatever it's worth, on a 37-mile flat route where my average speed is in the 16-17 mph range on my racing bike, my average speed is in the 14-15 range on my trike (riding solo in all cases). I'm still pretty new to riding any type of recumbent, and still developing my 'bent legs; from what I've been told, a trike is about 1 mph slower than a bike, and judging by my rate of improvement that seems reasonable—pessimistic, even.

I got my trike for long-haul touring myself, although I'll just be using panniers, no trailer (consider that if you get a 2-wheel trailer, you've got 5 tracks on the ground). I can confirm that all the little aches and pains that tend to accumulate in the neck, wrists, shoulders, and back are absent on a 'bent trike, even after 60 miles that include 20 miles of the roughest, washboardiest chipseal that I can find. So I don't think a 'bent is faster, but it may leave you feeling fresher when you get where you're going—that's what I'm counting on, anyhow.

Descending is fun. I've always said that racing bikes are mostly steered with the hips—you don't really want much input on the handlebars. Obviously that's not true with a trike, but when you're descending fast, you really need to get into a zen state of mind where your inputs are smooth and minimal. Flipping a trike at 45 mph would not be fun.