I would say, dbs are nor so much relevant. Difference between different antennas is a few db, and 2-3 db doesn't make a any real difference in data transfer speed -- what plays much more role is SNR, AP sensitivity and noise level, dynamic range, speed choice algorithm, etc.
Antenna pattern is important just to understand the pattern -- which is more or less omnidirectional.
Ruckus AP are good because they are good in many areas -- good sensitivity, efficient interference prevention, active antenna optimisation, efficient polarisation diversity, etc. Each adds some benefit, and result is more than each part itself.