I'm in a similar situation. I'm leaning to the 625's for my softale 107 I'm putting together, because with my combo and riding style.... love low and mid torque more than 5000 plus RPM nuts. The 625 was designed around a softale/B motor medium weight bike that stays under 6K rpm. I think the 525 would be real sweet, but a little finiky to tune it in at the higher static comp.
As of right now, I'm going with the 107 Axtell kit ( cyl bore, 20 deg. domed pistons, HTCC head recondition), Horsepower inc 55 mm thottle body, TMan TR625G cam with the hyd conversion kit, Baisley Roller Rocker conversion
Tune by Bean this spring
02 FLSTCI 117, Darkhorsed, Baisley Pro-Street Heads & corrected geo. roller rockers, Axtell kit 20 deg. rev. dome pistons 11.5:1, HPI 55/58mm MaxFlow tb, Tman TR-662-2 & 3 stage pump, Boarzilla, Barnett Scorpion clutch, Jag 10 row oil cooler, tuned w/ Twin Scan II+/WEGO IIID
10 Ultra Limited 103, Andrews 54 cam, SEAC mod breather, Bigboyz ported heads @10.2 comp, Jackpot 2-1-2 header and Dyno tuned muffs, TTS, tuned w/ Twin Scan II+/WEGO IIID