I read somewhere, may be creditboards or some forum.... that TU consider cards with CL more than 10k as prime cards. Is that true?
Can a CB have their own rules in FICO scoring system?
Where did you see that? Fico takes in consideration the utilization and I can assure you that my score was equal with two cards of less than 5K with same utilization. Now with multiple cards and same util I doubt this will make any difference. The main factor I would say is utilization and if you try to achieve 800+ score it can be done with lower limit cards with no problem ..just pay attention to util, let 0 balance report on all but 1 card and that one less than 10% and time time time... this will get you there no matter what credit line. At least it has for me 
... and of course no baddies ever !
Will share the link if i find it again... I too dint find much difference in my TU score with the other 2, just a point or two