However, take the flipside of that coin: I'm a knackered Cambridge MEng stude, and I'd feel comfortable talking electronics, or systems, or control, or structures, or materials at a level comparable to a 'pure' student of any of those disciplines -- as well as having a better-than-average grasp of Aero itself -- my Part IIA (third year) aero exams at Cambridge were easily comparable to the 3rd/4th year Imperial papers I've had sight of. The first two years of General will make you a very employable candidate at the end of the four year course; plus you'll have 'the name' of Cambridge behind you.
Plus I discovered I quite liked control theory; something I'd probably not have studied unless I'd been 'forced' to sit down in front of a lecturer and study! It's making up a fairly sizeable chunk of my Masters project...
Of course if, like me, the thought of studying wiggly amps, wobbling beams and other 'white man's magic' makes you chill to the bone and you want nothing more than playing with wind tunnels, then Imperial might be best for you.
The other thing is, of course, that you don't have to live in Dante's tenth circle of Hades, London... Having lived just outside the M25 for 18 years I had no intention of living in London if I could avoid it -- Cambridge is a *much* nicer place to live, IMHO. Also, the teaching style is much more personal -- with supervisions in pairs (three hours a week, at least) and labs in groups of no more than 8 as I recall the first few years.
I'd say:
If you're keen on aircraft and want to work in the industry: Cambridge
If you want to end up in the City or similar, and just quite like aircraft: Cambridge
If you want to go into research/a PhD etc: Cambridge
If you absolutely, positively can't stand anything other than aerodynamics and aircraft: Imperial (but then also, on a par, Bristol and possibly Soton. Bristol IMHO is a better department than Imperial)