I am installing an Icom 802 ssb with a 140 tuner. I am looking for
advice/experience on the difference in performance between
Shakespeare's 17'6" whip vs. the 23' whip.

I have a sloop with a split backstay and probably will go with a
whip.I only have about 3' between the antenna base and the mounting
clamp on the transom. Insulating the backstay and running the feed
wire along the split (through the bimini) is my second choice.