The A139 cables are much thinner, but you pay a little extra for that.
As Viofo said, the T130 cable is similar to the A129 cable, although with a different connector, so not the same.
It is quite a nice size, I wouldn't want it any bigger, but given the adjustability on the interior lens it is a sensible size, and with a 3 channel you can't have it too small or it would overheat. Seems much easier to position than the B2W in the vehicles I've tried it in, although in some vehicles the B2W fits very nicely. It is a higher quality/resolution product than the B2W anyway, so I'm just comparing the shapes. Also quicker to position than an A139 since there is only one unit on the windscreen, so more suitable if you are likely to be changing vehicles, or if you prefer the alternative styling, or if you want to record people at the window with the adjustable interior lens.