Honestly, of all the puffers i've personally kept, i almost miss my Congo the most... i would say if you can get lucky and go hunting for one in person, try and find the most active one you can find...
My one used to actually come out of hiding and up to the glass when i used to go near the tank, after a while, my congo even sort of worked out when it was feeding time... definitely a very interesting puffer to get IF you can find one that doesn't just bury itself all day every day...
Otherwise, what about some of the other smaller active species of puffers such as the C.irrubesco or C.Loreti?
They are C.irrubesco isn't quite as aggresive as the loerti if i remember correctly, but both have some nice patterns imo...