Favors is not better than Asik. He has got potential to be better but right now Asik is the better player. He can run without breathing in 2nd fastest tempo as being 7 footer, staying on the court over 30 min without foul problem, averaging double double in every match without using any ball, rebounding in crazy rate ( 3rd in league, 2nd in percentage) and creating perfect defensive difference even though he's playing with really bad perimeter defensive players. He's one of the best post up defenders but also pick n roll. His lateral quickness, smartness and timing is just rare.
And for Al jef, i think he can not be the answer for the Rockets due to his motor. Houston is playing small ball, run run system with sharp shooters + perfect goal keeper Asik. They look for Howard if it does not happen, a PF who can stretch the floor for Harden and Lin. Millsap can be better player for them.