My impression from watching their works is that Risa does better with a more powerful, more serious role, while Ai is more natural. Mano has the look and the aura of an actress, but I would rate her acting lower than Ai and Gaki at the moment. Heck, she did not have to do much in Minna Esper da yo. Patlabor really does her good, but the movies are really niche and shallow. Mano role is very standard too. Regardless, Risa and Mano show very strong wills and passions for their career. Risa wrote many on
her blog that she really love and want to do stage acting. And Mano said in
this Patlabor interview that despite seeing her senpai in variety and stage play, she really want to act for film and TV series and leave the work as a result of her effort.