I'm a big advocate for soft plastics and I've always found them to be perfectly suited to kayak fishing for a number of reasons. Most of you guys already using them know that they can catch almost anything, and will often outfish bait. Thats the most obvious advantage, but another that I really appreciate is that it minimizes what you need to take with you. I typically only take a handfull of SPs and jigheads in a small waterproof container that fits neatly into a pocket on my PFD.
And because using them is simpler than messing around with hooks, sinkers and bait, it's more efficient and far less fiddely to be using them in the limited space you have on a yak.
Another big plus is that they usually only ever seem to lip hook fish, which means unwanted fish typically get returned quickly and relatively unharmed.
And for some reason, they don't seem to be too attractive to rays or sharks, and given I don't target these, helps to reduce unwanted bycatch for me. Another advantage - although this is rare - if I don't happen to catch fish, I don't end up with the stench of fish all over my hands.
One last reason why I like SPs so much - and this has nothing to do with yak fishing - is that being the conservative minded guy I am, I really detest commercial fishing practices (specifically netting). This means never ever buying bait. And having SPs handy when no other bait is around fills the gap nicely and is certainly much cheaper than buying pillies and the like. Having said that, I do often fish with bait if I'm going for big snapper, but I generally only use bait that I catch myself. I do use berley in these instances to, but again, only from fish carcasses that I put through a heavy duty meat mincer. Works better than any bought stuff I've seen.