both have models for X and S band now, I wouldn't go with just an X band now that the others are available. Apparently many ships turn off X band at sea and just use S. SeaMe (Munro is the name of the company) will ship you one from Britain on a credit card, that't how I got mine. I believe Echomax is distributed in the US now - if not I'm sure they would ship one as well.

In a recent comparison by a British magazine, the Echomax came out a little better, though both work pretty well and far, far better than a passive reflector, almost all of which hardly work at all according to about 5 published tests.

The average draw is pretty low, about 200 ma if I recall. They both have an indicator light which warns of a "ping". If there are only a couple of radars in the area you can get a good feel for how many hazards are out there by looking at the flashes on the LED. The SeaMe (and probably the Echomax) have a remote capability, I mounted another LED at the binnacle to warn of traffic.

You can use it while your radar it on, they suggest NOT putting the transponder antenna directly in line with your own radome - could damage it or at least make it inoperative by flooding the front end. I mounted mine on top of the mizzen, directly over the radome by about 20 ft. One thing that WILL happen (and is mentioned in the manual) is that your own radar will trigger the indicator light, so that as long as my radar is transmitting the LED is lit solid - making it useless to detect other traffic. This will happen no matter where things are mounted, there is always enough leakage and side lobes to do it.

I have some reason to believe that it makes our boat quite visible, but I have never done a quantitative test. The magazine and safety authority tests have been pretty conclusive however.