I know some folks like short scale for the pure geometry vs. their build or injury or whatever.
That aside, is there an advantage to a short scale over a long scale?
Reason to have both?
Trouble going back and forth?
Curious as to why one would add to an otherwise ‘long scale’ arsenal.
I bought a short scale 30" Gibson SG bass over a year ago and I just didn’t like it. My hands are small to medium sized, and I really tried to like it, but every time I played it I couldn’t wait to get back to my 34" long scale Squier. . . 
(I should have listened to @terb . . he tried to warn me!)
The Gibson was a bit easier to play (because frets were a little closer together), so that’s one advantage for choosing a short scale, but I didn’t like the chunkier neck and it didn’t have as much sustain as my Squier.
I just thought it might make a good complement to my Squier: long scale vs short, maple vs mahogany, roundwounds vs flats, heavy vs light . . . 
I’m sure other brands of short scale basses would be brighter than the muddier sounding Gibson, depending on the location of the neck pickup. I also didn’t try it out in person before buying on-line . . . lesson learned: I won’t do that again.
YMMV
Joe
check out our short love thread
but short 
answer, they sound a little different, some people find them easier to play (me), they’re lighter, they’re something a little out of the ordinary. they’re fun! I don’t find it difficult to switch, ymmv.
They are fun!
I have both short and long scale basses and switch back and forth regularly with no problems. My #1 is a short scale Mustang PJ because the neck fits my hand better than any other bass I’ve owned. The fact that it only weighs 7 pounds doesn’t hurt either.
@John_E I played long scale 5 string exclusively from the very start of my bass journey, and was even a bit snobbish about it. “I’ll never play a 4 string. I’ll never play a short scale” was my mantra. But then, a funny thing happened…
A couple months ago, I got a Hofner, which as you know is short scale AND a 4 string. I immediately fell in love with playing it! There went my mantra out the window. I’ve since bought another short scale 4 string, and have sold my long scale 5 string.
I love the short scales for their lightness and ease of playing. To my ears there’s not enough of a difference in tone to matter.
My new mantra is, “I love 4 string. I love short scale”.
They’re just cooler. It’s science / fact 
Shortscale is much more comfortable to me when playing in position 1 at the first fret.
I have both long and short scale basses which I play regularly and I have no trouble going back and forth. My short scale Hofner is what I use for my Beatles covers and I love the tone it produces.
I have two long scale basses (Squier PJ, Sterling Ray 4) and one short scale (Gretsch Junior Jet). Each one has its own distinctive sound. I like having a choice whenever I play, and have no issues switching back and forth between them.
@howard hit the nail on the head - playing a short scale is fun! When I just want to play for entertainment (as opposed to serious practice, learning new songs, etc.) I usually reach for the Junior Jet.
Of course, that fact that it is considerably lighter than the others might also be a factor. 
I tried a short scale and yes it was fun but I found myself reaching for one of my 34 scale basses almost every time I wanted to play so I sold the short scale to a nice young fella who will certainly use it rather than it gathering dust
I should add that I have 4 basses and all are different scales, including a full scale bass. not everyone wants more than one bass, but you can play both if you want, obviously.
Like others, I have no major problems going back and forth. My short scale (Serek Midwestern 2) has a bit more ‘focus’ in the low frequencies, and the long scale (Warwick Streamer LX) has a bit more clarity and definition in the highs. But they both also have their own signature tone. If I had to pick just one, the Serek (weight, portability) would win out by a hair.
Just one more thing to add to this.
I know guitarists that prefer a short scale, because it is closer to a guitar scale.
For me personally though, I prefer long scale, even though I know it’s not quite as easy to play.
sereks are cool 
actually I hear tons of people say they find long scale easier and short scale too cramped. to each there own blah blah 
True, but I have the hands of a child. 
My hands work well on a violin, so I don’t think the short scale would be too small for me. But as you say, for some I can see that being the case. Even from Jazz to P necks.
Are the parents of the child aware?
Ouch 
