IMO, the Askoll motors are more efficient and of higher quality than the eheims. Eheims are like an old Mercedes... you will never hear me talkin' trash about them, but there are newer and better things out there. Eheims for instance, aren't the quietest or coolest running even (Aquamedic Oceanrunners make more flow&pressure for less electricity if I remember correctly, and they cost less). One Oceanrunner 6500 would work well here, and cost less.
The one thing I dont like about eheims now is how expensive they have become. When the 1262 retailed for $120-ish, it was a good buy, but now I see this thing listing for closer to $200. IMO, you should just buy and mod a Laguna 1500, or buy the 'ready to go' version for just a little more from ATB. Now, I used to score Laguna 1500's a couple years ago for about $100, and now I know they are more, but still... if you look on ebay, you can find them for $100 here and there still. Or, just get the ATB and dont worry about it. Considering what the eheim 1262's and 1260's go for these days, the 20 or so extra bucks buys you a much better pump.
As for differences with the ATB and Red Dragon... none really, just price. There might be some slight spec differences, but thats about it. The materials are the same. I know there are claims by RE out there of being better due to a 'custom motor' or 'Titanium Shaft', but this is BS. Askoll doesnt make custom motors, and the Titanium shaft is a costly and unwarranted option only. OTOH, with ATB, you get some great service that leaves RE in the dust.
Here's some history... how I and some others got to the bottom of what a Red Dragon really is and how to 'DIY' some great Laguna/Askoll based motors. I spec out the motors and how to make the pumps (mostly for skimmers). Since then, there has been a 'boom' of Laguna based skimmer pumps, to say the least...
DIY Red Dragon Pumps, gathering ideas. - Reef Central Online Community