7 meg network faster than 21 meg network?

[Chicken Boo]

I've got a white speedstick (7meg network) and a black one (21meg supposedly). At home the white stick gets slightly better speedtest results than the black one (about 3meg down, 3 up on the white one; 3 down and 1 up on the black with far worse pings). Putting them in the same machine, same position. Do I have a dodgy black stick? Dodgy tower in the area?

(I just checked now and at work the black stick gets better results (5 meg down, 3 up, good ping), but still nowhere near the promised speed)

 

[h0ll0w]

http://www.united-distribution.com/products/bodycare/images/speedstick.jpg

 

[FrancTheTank]

http://www.united-distribution.com/products/bodycare/images/speedstick.jpg

So helpful

It's probably the antenna on the speedsticks may be slightly different and thus in an area where the signal is not 100%, the 7Meg stick may operate better.

 

[sajunky]

Small differences can be due to the sensitivity of receivers or unsuccessful attempts negotiating faster speed in this location. This also affect ping.
It could be the various reasons, signal strenght/quality, or even tower not HSPA+ capable. Black modem can go faster, but only if signal is good quality. In other location black modem shows that nothing is wrong with it.
With MDMA you could see RAT window whether is changing to HSPA+ when black modem is exchanging data. It is changing at work, sure, but does it change @home? If it does, network allows go faster, but signal is poor.