False economy is the point ie you might not think that you will ever need a
sliding compound mitre saw but those who have bought a basic chop saw in the
past will probably tell you now they wish they had bought the sliding mitre
saw because it gave more flexability,depth and wideness of cut over the
stationary fixed height and width chop saw.

No - in the 3 or 4 years that I have had the simple chop saw, I have
had absolutely no need for a sliding one and no desire to find an
excuse to buy one as the OP is looking for. OK no doubt there is use
for the sliding compound mitre but I've never seen any and I have my
suspicions that like all tools, cameras, computers, stereos, etc.
with multiple facilities, the more exotic ones get use about once in
the item's life. Gimmicks IMO.

Rob