Bigger ... is better ... (as a rule of the thumb)
Sure and taking it to the extreme we end up with something humongous like the Zeiss Otus. To get this 5% better quality you end up with a design 2-3x larger/heavier and 4-5x more expensive.
Of course, it's a gross exaggeration, but I believe there is a "good enough" threshold where it would be difficult (in real life) to distinguish pictures taken with an excellent lens from a good one while the good one would be quite a bit smaller and lighter.
For instance, I'd be happy to pay more for very good compact designs.
When going through my favorite shots from 2013 and 2014 (so far), I noticed an interesting side-effect related to this. During 2013 my gear was full frame (D800) with plenty of large, heavy lenses. Since November 2013, I fully switched to MFT.
Very few of my fav shots were captured with the FF gear. In fact > 85% of my preferred shots were taken with MFT. The reason? I shot much more than before. The reason is that I enjoy it much more and the small package means I carry it with me most of the time. No more hesitation "should I lug around my gear or not?".
While being fairly evident, it's an interesting observation and I didn't think the difference in terms of usage would be so great.
Finally, here is an example
of very small design (albeit not bright). Take this and a 12-32 and you're covered from 24 to 200 (FF equiv) in a tiny MFT package.