i think every betta is dif...they are all great...and i think all the males are aggressive to some degree.. you should never put 2 males together . i had a CT male he was calmer but wold flare at everything...he died
..now i have a VT boy hes super friendly with me lets me hand feeding him and will swim in to my palm.. ne doesn't flare unless i use a mirror... few days ego i got a ghost shrip but my boy killed him with in 2 days
...So i think they are all different but most males will be aggressive ..if you looking for whats compatible with bettas look in the compatibility forum, and bettas are not expensive at all unless you get them of the Internet and are specially bred.. at the pet stores they go from 2$-5$..well thats here in NJ.
good luck finding your perfect betta!
and remember the fish maybe cheap but you do need spend some money on good quality food,fiilter,heater,plans..tank..so keep that in mind!