I really wasn't sure what you meant at first. If you're referring to my "in the know" comment, I wasn't directing an insult at the responders or suggesting they weren't knowledgeable. What I meant was that when I started the thread I was hoping that in these forums I might get responses from people who worked in the industry or for different ISP's or simply people who knew a lot about what's available. It had nothing to do with them, I was simply explaining my intentions (and agreeing that everyone posting their individual experiences isn't the best way of going about it). Don't be so sensitive, it's only the internet

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I thought it might be obvious if ISP A has latency of 100ms (in this country), or that doubles at peak times, whereas ISP B has rock solid latency of ~30ms 24/7. For example, with regard to dial-up, everyone seems to be agreed that AOL has worse latency (from anywhere to anywhere) than most other ISPs. I've heard that certain things at the ISP can affect latency, such as old or inferior server hardware. Also, would the type of Centrals used make a difference (Ethernet faster than ATM cloud?) or the transits?
I understand the point that if I live at Land's End it would probably be better not to use an ISP based at John O'Groats, but as I don't live at either extreme of the country it probably won't make that much difference (please, correct me if I'm wrong; if you know roughly how much difference, numbers would be great). With regard to the target machine, surely that would only really matter if I was making a P2P connection with one other machine and then not using the internet for anything else (which I suppose I
might do if it was for business use or something, but it isn't, so I won't). In reality we use the internet to connect to hundreds, if not thousands, of machines all over the country and even the world. If ISP A's latency is 50ms higher than ISP B's, then surely whether I'm connecting to London or New York, it will almost always be higher. If it helps, I only really care about latency to Britain and Europe.
Thanks again.