Spec wise, I think its like any other bike out there at the moment ... certain price points = certain componentry levels ... and cube mainly fall into them along with any other brand.
Frame wise, I'm not sure, Its hard to tell from just looking at them. My brothers Peleton (2009) is sitting in my garage at the moment, beside my trek 1400 (2007). The tubing all round edges on the large size with the rear stays being fairly wide and sculpted so I reckon its going to be pretty stiff and leaning towards a tight, stiff and possibly harsh(ish) ride in the long run. That being said, a step up in tyre size would compensate any harshness considerably.
Build wise, I cant really fault the Peleton from looking at it. The welds are neat enough, but its not going to win prizes. There is the odd little dimple bubble mark in the welding, and its not been brazed / smooth welded which you start to find on higher specced frames ... but lets be honest, if its welded together tight, does a smooth weld make you ride better? no.
What the dealers may be talking about regarding better frames down to things like the tubing used. The Aerial / Peleton use double butted tubing, and the higher end frames use triple butted tubing. Its all to do with how they form the tubes to be thicker walls at the joint ends and thinner in the middle sections ... improves weight / strength / stiffness etc. But I dont think that at the price point of something like the Peleton, you're going to be getting significantly better frames. In fact, reading up on Trek's 1.5 frame, which has Alpha White tubing, says that its likely to be plain guage simple tubing, where are the Cube Aerial ( similar price point ) states it has double butted tubing. On first glance, the Cube would appear to read as though its got the better tubing.
At these price points, the differences in frames are going to be outweighed by wheels and gears and other kit I think.
Personally, my thoughts are that first and foremost get a bike which fits you and then get one you like the look of too. There is no point getting the bike which a dealer says to you " this is better, just because " when each time you ride it you're thinking " but I really liked the look of the ????, I wish I had got that ". I'd say get the bike which is going to make you think " I want to go out for a ride on that "