In my opinion, Acer and Advent are the less reliable.
As I used to work for Currys (I know, but it was a nice little high street one with very friendly staff!) I used to be left to deal with the laptops.
Mainly sold Advent and Toshiba, but also stocked Compaq, HP, and the occasional Acer and Fujitsu. Had one Toshiba back which the external AC adaptor failed on. Advent? Quite a few back. Problem with Advent is, they aren't an actual brand name. Packard Bell, another DSGi make, is actually made by NEC. But Advent? It's a name that DSGi (Currys, Currys Digital, PC World) stick on any laptop they find.
I'd say if you get a cheaper Toshiba you'll be OK, or a Compaq (part of HP). Neither will have as much 'spec' as the Advent or Acer, but they tend to be solid, and the Toshibas have a little street cred as well

Compaq are a bit 'boxy' normally, but they are easy to work on from both a 'using' sense, and an 'upgrading / repairing' sense.
I wouldn't touch Fujitsu Siemens with a bargepole. It's just my opinion, but the amount I used to get back with things like HDD failures was unreal. It was the cheapest models (£399ish), but that's no excuse. I'd assume the main cause was overheating, not very deep units and a pathetic little fan and a tiny air vent.