Mamby by decision. He had the height, reach, and defense to keep Ricky on the outside. He also had the chin to take anything Ricky hit him with. He had great stamina too.
I'll go with Hatton. Billy Costello ran Sweet Saoul out of the ring and battered him petty bad. Hatton UD.
That was "old" Mamby almost two years removed from holding the title and he took the Costello fight on a few days notice. Prime Mamby went the distance with prime Duran and easily beat Esteban Dejesus.
Mamby had a nice run for a few years there, which coincided with his title run, but I'm not sure he was all that much a better fighter at that time -- he was always competitive with very good competition and a shade below the best. I'll still go with Hatton: a swarmer isn't going to be sitting back mesmerized by Saoul's cuteness.
Hatton would outwork him more often than not, but would be made to look bad in the process. Dejesus was finished by the time Mamby beat him.
I'd Fancy Hatton, Saoul is real cute..particularly with those who will seek to "Box" with him, If he cant Hurt Hatton, then their will be no Brakeman on Ricky's Train, but this does not mean Ricky would be Like Katsidis, Ricky on his way up used very educated pressure, His Trademark Scissor-Step Allowed him to be streight back on an opponents chest in an instant, he was very good at cutting the ring also, Saoul did not get the rep for giving most quality guys trouble for nothing, Ricky would be in a Long haul Track-To-Whack Campaign, where many were looking for Saoul's Head, Ricky would of course be laying down a foundation with that Left Hook to the Body, Another Weapon Ricky has against "Mobile Boxers" his his ability to "Rag-Doll" Them.. He has been much criticized in the past for Pushing and Shoving his opponents about in the early going, and indeed it may not look very tidy, ..But i suspect if you are on the end of it, you are feeling his strengh and if he is treating you like a Pitbull with and old Slipper... then it can be intimidatory.. more than once has an opponent come in thinking he can Out Finesse Ricky.. by the fourth round, after being Mauraulded, They get a look in their eyes..And expression.. Damn i might not even go the distance here... I will give Saoul the benefit of the doubt, although he might get a few warnings for excessive holding, He goes the distance... But the Hatton - Pattern wins clearly,