I believe this actually figures in with Bruce's explanation in The Avengers about always being angry.
Until the battle against Abomination, Bruce has always been fighting against The Hulk - trying to restrain him mentally. Once Bruce grudgingly accepts that The Hulk is a part of him, and decides to use his abilities as the Hulk, he has much more control over him. He can now concentrate on attacking just Abomination, or just attacking Loki and the Chitauri.
Blonsky, on the other hand, was specifically seeking Abomination and the power right from the get-go. He wasn't trying to control Abomination, to the contrary, he was specifically trying to make him stronger. By embracing Abomination, he achieves a greater degree of control quicker than Bruce had.
It should also be noted that Abomination and The Hulk were created in two dramatically different methods.
The Hulk was created in an accident with gamma radiation.
Abomination was created via a combination of old Super Soldier serum and Banner's blood. While both resulted in giant rage beasts, it is not entirely fair to do a straight comparison between the two and expect them to be identical in all regards.