Testing the I9300TDULF2 on Vodafone in Australia here.
Downloads seem to be roughly the same speed as the stock modem (I9300TDULE6 shipped with my device) @ around 110kBs per second.
Uploads varied greatly (anywhere between 200KBps on the stock ROM to 50KBps).
The TDULF2 was more consistent, with an upload speed varying from 55-75KBps.
Wifi range seems to be about the same.
Overall speed seems to be about the same.
The signal strength on the I9300TDULF2 hovers around -99dBm to around -110dBm and ranging from 1-8asu (have no idea what any of this means, but thought I'd include it).
The stock I9300TDULE6 does much the same.
I think a lot of these numbers are not conclusive though as the weather here (in Sydney) is terrible and clearly affecting reception. Also, where I live, doesn't pick up the best reception from cell towers anyways. Probably best if I tried to compare the ROMs in the CBD.