I don't have much experience with iPod docks I'm afraid. Bex has an iPad dock, but I bought it for about £15 from Sainsburys - just an own brand thing... I wouldn't recommend it for sound quality!
On the other hand, one of my mates bought a Bose iPod dock a couple of years ago and the sound was fantastic - but I think it cost around £200 (so you'd expect it to!).
Having read up on the two products you linked to, I'd be tempted by the Sony (unless the recharable battery of the Logitech one is any use). They both look good
Checking it out in store sounds like a good plan. Is there a
PC World near you as you could check out the Logi unit there