While long tails might be pretty they're usually pretty impractical thanks to how they like to drag along the ground as you walk, and that that floor usually isn't as clean as it'd seem... (If the tail has white fur on the underside it might quickly turn grayish if you let it hang and drag after you too much) Having to walk around holding a tail all the time is also pretty impractical... They also take up more space if you for example would like to sit down or when transporting them.
If they're made correctly a tail can be both long and big without dragging along the ground... But most of the other annoying things will still be there.
Personally I prefer slightly shorter tails, partially because of the reasons listed above, and also because I'm pretty short myself x-x
As for what is best, I'd say a short tail have the upper hand here, but I guess it's mostly a matter of personal preferences and how much time you're willing to spend looking after and making sure your tail won't get dirty...
