I have that velleman, i find it a bit dark and hard to read while working on the cars. cheap n cheerful though, i usually carry it around with me if i'm working on location.
The second one is more like the picoscope in that it has reference material and automotive related.. but its only 1Mhz 8 bit though, thats pretty low.
A four channel scope might be more useful for car work, we have a TDS 220 and a picoscope 4 channel in the shop for collecting traces, but primarily work on 4 cylinder cars.
I'd probably go no lower tham 10Mhz and no need for >40Mhz (for nearly everything car related), long capture buffers are useful though.
I think the picoscopes are overpriced though.
I'm rarely with a car without a laptop, so its never a problem. The netbooks work great, big clear screen and lots of reference material, plus all the diag tools. A picoscope+netbook probably weighs about the same as that second unit !
they have a lot of support and forums too which is going to help, they're a popular automotive scope.
You could probably find a used portable DSO for similar prices, like the TDS 220 etc.