I recently replaced my 3 SmartBridges APPO APs with MT 532/Ubiquiti card APs. All is well, except typical upload speeds are now about 1/3 of what they were with SB. 95% of my CPEs are still SB2100s, and I’m also seeing the same slow upload activity on the 5 NanoStation2 CPEs I recently deployed. Before the change, I typically saw upload speeds always equal to and sometimes 2 to 3 times faster than download speeds, but now upload speeds are always 30% or less of download speeds. I’m BW limiting in the MTs, tried to do it both up and down, but the up doesn’t work. So I tried disabling the ‘up’ BW limiting, thinking that the MTs might be trying to do something they can’t do and losing BW doing it, but that didn’t help either. Any ideas? Thanks.
My upload speed is 12-15mbps TCP and download is 5-6mbps 
, at one link.
you probably have different tx powers and rx sensitivities. the sb might have a lower tx power and/or the ubiquity might have a lower (worse) sensitivity, so traffic SB >> MT falls back to a lower data rate, while MT >> SB operates at a higher rate.
compare the rx level at each end
The limit client TX (=upload) option in the MT AP only works if the client is also an MT unit. If not the MT AP can only limit its own TX (=download) towards the client.
Why your upload is not as high anymore as before is probably to do with the higher output of the signal from the new AP’s Ubiquity cards. They are much more powerfull then the SmartBridges and while you might think this would then improve the radio link it is actually overpowering the radio’s of the clients.
Try to play with the radio output settings on both ends. Make them actually as low as possible while still having a reasonable link towards all of your radio’s.
Lots link (and therefore speed) problems are caused by too much power of the radio’s.
rgds.