ss+el:Transformers are only violent if your child knows the stories. Otherwise, they're just a cool toy that is two things in one. Given my child's cluelessness toward either, I'd choose the Transformers over super heroes.
Ditto this answer. Even super heroes can have violent storylines. My personal preference is super heroes because I enjoy playing them with my son more than transformers, but either are fine with me.
Both Transformers and Superheroes will encourage fun, exciting, adventure-based pretend play. Both will also potentially call your child's attention to a brand that is being marketed to boys as young as 3 or 4 and as old as 13 or 14. Just be prepared to explain why not everything of that brand is okay for him to watch or own.
Steel yourself, because it's likely that you will have some variation on this conversation many, many times over the next several years of your son's life, as influences from friends, school, media, and marketing become more and more influential.
ss+el:Transformers are only violent if your child knows the stories. Otherwise, they're just a cool toy that is two things in one.
Mine went through a Transformers phase and to this day have never seen the cartoons or the movies. A lot of their interest was sparked by kids in school with older siblings who did know the stories but the play on the play ground remained fairly docile.
When they come with guns or weapons I take those away. They didn't seem to care.
Just be warned that the more advanced Transformer toys take a freaking PhD to transform. Never has a toy made me feel so stupid. They actually caused more frustration than fun in some cases when the kids couldn't transform them on their own so be sure to buy the easiest ones on the market.
As for choice? It's not really my choice, it's theirs. They were interested so we went there. Mine have never really gotten into super heroes but if they had we would have gone that direction instead.