automatic advantages

i have been in this hobby for around 8 years now and i have through quite a few cars, mopar only......well in this time i have never ran an automatic before....i used to buy manual cars only or i have 4 speed swapped a few cars too.. so my question is: i am considering building a 74 duster and im not sure about what driveline to use.......Automatics are new to me .....so i am asking if there are any advantages that torqueflights have over a 3 or 4 speed.....so far the big advantage i see, is that automatic stuff seems more common and easier on the purse over 4 speed stuff. any input please......BTW i am not sure what engine i am going to use....50/50 toss between a 225 or 360.