I've bought a 660 recently, and do like it for several reasons besides the fact it was cracked and available at a considerable discount. I was having a log jam of my left hand fingers on the higher frets while playing La Catedral on a 650, and this was the main reason. And Cedar top is nice for that built in Reverb pedal sound! (In small doses)
So I found that it is more comfortable to play at the higher frets for my left hand, and it's slightly wider neck is a bit more comfortable for my right hand. And it has a nice D taper to it's neck profile.
I have fat fingers and bit above average span, so that was also important.I wouldn't have paid full price for this scale length however (unless it came with free coffee for a year or something.)
I believe the 660 is more common in Flamenco, and also replicates Segovia's guitar? (I could be wrong about that)
One thing Flamenco players will do is Cejilla or Capo the first fret.
I like to tune my guitars down a bit- half steps or whole steps, and a longer scale helps in this regard when using higher tension strings. However, higher tension strings aren't a requirement by any means. In fact you could use lower tension ones just as well, and might be better off doing with medium or low tension if you tune A440.
A higher tension string on a longer scale will put more pressure (or is it stress, torsion or strain?) on the neck and soundboard. If it's a vintage guitar, that's certainly something to consider. I would personally hate to put too much tension on an old guitar and warp it's neck or soundboard too much.
If you have above average to large sized hands you probably won't notice a huge difference, but in fact might like the added width for comfort of both hands, while plucking and also while fingering.
That being said there is more to all of this than just scale length and neck width, as neck profile is also important, and is, sadly, more often than not, overlooked in Classical Guitars.
For example I could not comfortably play a wider 660 with a fat C shape neck, and prefer a D or U shape. Obviously to each their own, but as previously mentioned, you can always have a new nut made if needed.
"I can sense the atonal...I always try very hard to bring it out."
- Julian Bream