Recommended Tests

 Well if it were me, and I had tested at, or above my ISP cap, then I would leave it alone, (if I had done all the adjustments that I could) unless one had features that I needed that the other one didn't.

 Or I would use the one that was most recent. But that doesn't always mean more efficient either. lol

 The DSL company will surely bring out a modem when they do the install.  You can't just switch out a modem, the MAC addy has to be set in the ISP's servers, otherwise the data will have no idea where to go. Kinda.

 When you first get DSL, they tell you NOT to unplug the modem for a specified period of time, this allows there servers to regulate the distance, and performance, and plenty of other things I have no idea about. So once they get it installed, leave it alone, if you don't , then you'll never know your full potential of bandwidth, from the way I understand it.  There will be a huge sticker on the new modem they bring that states this.

 When you switch the modem, your going to have to call the ISP, and tell them the make, model, and MAC, they must type this in, or you will have no connection.

On Telus DSL in British Columbia. They have automated the modem's MAC address authentication. Plug in and start surfing. It is good for two MAC address's. And I think the unused MAC address will expire in two hours or so. But you can interface with the website to delete MAC's if there is a problem with an old MAC not releasing.

So when the day comes to get service, there is about a day's worth of unstable speeds, unless the tech did not have to go to the node to switch you on to a different port for a higher speed package. Since DSL is slowly upgrading to faster ports. And if they run out of higher speed ports for new customers? Well tough, till some upgrades are made to remove the older cards.

And Telus also likes to give out a combo modem/router to alleviate call supports dealing with a modem and then a router of the customers choosing. So since the Siemens Gigaset SE567 was a piece of crap with the 'Telus firmware' version. I now have a modem only, Thomson Speedtouch ST516v6 , And my own router.

And if the DSL modem can not train(stay connected) to your faster speed package, due to line noise or distance, support can throttle your speed back to achieve a stable speed.

And some DSL ISP's have only certain modems that work on their particular DSL setup.

Maybe cause I'm kind of sleepy right now. Chocolate bars and cookies are wearing off.. Thought I'd Google  Man Loving . And this is not a photoshop.