deca actually has very low sides compared to other AAS.
but what happens is guys fail to run the proper ancillaries on cycle. and the estrogen and prolactin build up are the things that end up giving them sides. and its a domino effect. water weight from estrogen will lead to many sides happening.. insomnia, high bp, high HR, feeling lethargic. and then the prolactin sides of deca dick and gyno.
but don't mix up the sides from deca vs. the sides from the estrogen and prolactin you are getting.. its like driving a car and not changing the oil ever, having the engine go bad, then saying that car brand sucks. had you done the proper maintenance on the car you wouldn't of had that problem to begin with.
if you keep the estrogen and prolactin at bay then you will be fine. and don't forget support supps as well. newbs don't know the difference between prolactin and Tin actin, hence they shouldn't touch deca.