For a tuner that is to be used in a hi-fi set up, a balance between good sensitivity, noise filtering and sound signature is very important. This is an aspect which is very hard to find in the right combination. From my experience, tuners with great sound quality usually have lower sensitivity in order to keep noise and interference down, and also to avoid un-necessary filtering in the circuitry. Users are also expected to use these in areas where the signal strength is adequate and with a proper antenna (external, if required). On the other hand, tuners with high sensitivity (we hear these amazing stories of the tuner working without an antenna or with a small piece of wire as an antenna) at times suffer from overloading of the RF stages, especially if one lives very close to the transmission station and they are a bit loud and harsh (a lot of the mass market Japanese tuners fall in this category, but not all). Also users tend to use these tuners in areas with reception problems and they do work due to the high sensitivity but the quality of sound obviously suffers. Personally I have always believed, if one happens to live in an area with poor reception, then use a proper external antenna rather than opt for a higher sensitivity tuner.
Although I am a bit biased towards NAD, being a NAD-only user, I have tried other models, especially Marantz, Technics, Denon, Sony, Pioneer, etc. I have found NAD tuners, especially the 402 (and the 412) to have the right combination of these 3 aspects. Also, If the signal strength is a little low, but not awful, the 'blend' option on the tuner is indeed very useful. One can listen to a weakish signal without having to put up with mono sound (of course, if the signal strength is very low, Mono is the only option).
. The only tuner that I've found to beat the NAD 402 is the Accuphase T101 but then, Accuphase is in another league 
