Personally, the Mark 5 is the amp for me. My desert-island amp. It's the Swiss Army knife of small amps, and will do just about anything you can ask. If I needed more horsepower under the hood I'd be looking at the 35 or big daddy 90, but it'd still be a Mark 5.
Mark and Recto are two really different beasts, and full disclosure: I just sold my Mini Recto head, which is the same amp as the Rectoverb (without reverb of course).
Recto is old-school metal amp and does that ripping, tearing kind of high gain sound really well but it's a lot more limited overall. Mark 5:25 has 6 modes that all sound great and each mode is really versatile - even the "clean" modes can dirty up, and the Crunch mode does a sinister Marshall impression.