My current favorite is slow out - fast in. It makes less digital glitches than the default linear out - linear in and I can use relatively short fade times, even in ambience and overhead tracks where crash cymbals are loud.
 

 
What are your settings?
 

Added screen capture.

Mine is usually slow in/linear out. But I'll give fast in/slow out a go.
 
With vocals I always use slow in/linear as I like the slow in for breaths and linear out for the tails.

I find slow out / fast in to be almost always the best for a crossfade on anything. It's certainly what I try first in all cases, and rarely have a reason to change.
 
I also find it useful, where possible, to make the crossfade either very slow if between beats, or very fast if close to the next hit. Of course, a lot depends on the precision of the source performance.

Hi. I also think slow out, fast in yields the best results.
All the best.

Using complementary curves assures constant power during the transition, making it less audible. However, it depends on the duration of the crossfade. At short times below ~0.5 sec, you cannot discern any difference between fade curves. For long fades, I prefer a compound "S" curve.