you lose signal and noise at the same time. but, bi-cubic downsizing is also a noise filtering, it can reduce noise significantly. if you can design a filter by yourself, you generally don't go linear. because linear filters can reduce (i.e. smooth) signals a lot. you don't believe me, you need to go head to take some e.e. classes to study digital signal processing.

if you buy DC and like to have good one in dark light, you may consider FUJI.

when i got time, I will show you a picture taken in very bright light with my DSLR, 6MP, but very noisy. :((