If you want to run a few of the names past me I can probably tell you yay or nay - I used to work for Talktalk Business (and Tiscali Business before they got taken over) and dealt only with resellers and channel partners.
The main thing to remember is that in most cases you are using exactly the same wires and equipment to the property - very few providers have their own hardware in the exchange (you're talking big boys only here... Talktalk, BT, Virgin and Sky mainly - of those the biggest are Talktalk and BT) - The interesting bit is that both resell their lines/network to other internet providers... so smaller providers will actually be paying talktalk for the use of the line and equipment and you pay them and deal with them
Reason for lecture is that you need to mainly go with customer service rep... a fault can happen on any network and the only real differing factor is how well information is passed back to you... No-one can make the network engineers work faster (they work for BTopenreach - who provide lines to BTinternet and BTwholesale...same as they do to everyone else) - some are better at tweaking the profiles you are on to maximise stability and speed of your broadband - but on the whole it's customer service and price you need to weigh up.
If you have BT infinity where your shop is - GET IT!!! This uses the new fibre optic cables and the speeds are MUCH higher and the lines are far more stable - yes it costs more but it's worth it! Talktalk and other providers are just starting to join in the race but personally I would go BT if you can get infinity

And haggle!