Share you reasons/experience. I have a 3U BS09 and I love it, I was wondering if I should add a 4U BS09 as I find the 3U version not 'fast' enough for defence (c/f an NS9000X I used to use). or maybe I should just train more
Actually the singles/doubles divide is a very good reason to use differently weighted rackets - I've used 4U for doubles and 3U for singles (different rackets, though). I'm considering using a 3U Tantrum 200 for singles and 4U T200 for doubles, with some balance alterations.
I myself use a 3U Yonex Nanospeed 9900 for my doubles game and a 2U (same model) one for singles play. I'll be getting the 2U one soon and will string it with BG65 at 24x26lbs while the 3U racquet is at 2 pounds lower (both mains and cross) with BG80.