Thanks for everybody's input. I feel I should report back to the forum just to share my selection process. I hope it will be helpful for others regardless my decision is right or wrong.
I got the impression that the bigger the ball, the smoother and easier to adjust when use. so I narrowed down to 44mm ball heads. I was comparing Markins Q10, Photo Clam PC-44NS, Sunwayfoto XB-44 and DB-44.
I ended up purchased sunwayfoto DB-44.
From price perspective Q10 > PC-44NS >= XB-44 > DB-44. (I am in Canada, the price in the US and Canada are slightly different)
Load capacity perspective (yea now I know this number means nothing), PC-44NS > Markins Q10 > XB-44 > DB-44.
User feedback perspective, Markins is way ahead, followed by Photo Clam; sunwayfoto is not a famous brand in here. but I read the sunwayfoto discussion in the largest photography forum in China. Several senior members there who also owns Markins or RRS actually bought it and highly recommended it.
Funny enough, my finally decision on DB-44 was made based on something not so related.
1) sunwayfoto are made all metal (yes, the screw knot is metal finish no silicone). I somehow like all-metal stuff.
2) they have dealer in Canada and make the price as the same number as in the US.
I am still waiting for my Feisol 3401 to come. the dealer in Canada is running out of stock.
So, this will be my poor man's super comb. it's not the fantastic combination of Gitzo tripod + Markins ball head + RRS clamp. I will see how my combination works out when I am traveling in California this July.
Thanks again for everyone's input!
5D MARK II, EF 24-105, EF 70 - 200 F4 IS, EF 50 F1.4, EF 40 F2.8, ZE 50mm MP, EF 24 F1.4 Mark I, Leica R50F2, Canon G10, Canon EOS M with 18-55 kit, Canon FL58F1.2, 270EX flash, 430EX II flash. Manfrotto 055XPROB + Sunwayfoto DB-44, Feisol 3442 (No CC) + Sunwayfoto FB-36DDH2