I have owned and shot a number of different target air pistols over the last thirty years or so including recoilless springers, CO2 and PCP's - all of standard length - the last two being a Morini 162ei and FWB mod 44.
I can see no real advantage in shorter versions other than reduced weight which may be preferable for junior shooters etc, but the sight-base will be shorter which would be slight disadvantage (it is generally accepted that the longer the sight-base the better).
However I have borrowed and shot a short Morini and achieved very acceptable results so I would not like to make a recommendation. Shooters clearly use weapons which suit them and achieve acceptable results. Sorry I cannot be more helpful.
Aubrey