DS was a fucking nightmare at 3. Angry, sassy, occasionally violent, generally didn't give a fuck, along with being a bolter and quite destructive... He was also incredibly clingy to me and wouldn't let anybody else near him. He's now nearly 6 and has calmed down a lot, but still has his moments. School helped a lot! Still clingy to me but getting much better.
In comparison, DD was an angel at 3. No tantrums, walked along nicely, held hands, looked after her things, was generally calm and sensible, not clingy at all. She continued being an angel until she got to about 7, then the attitude started. 10 now and, well, she's 10!
I tried not to be smug about how well behaved DD was at 3, and yet it came along to bite me in the arse with DS. I still don't know where he came from.