Why must it be one or the other? I selected SP101, because some guy, who designs grips at Ruger, seems to have hands shaped just like mine, and because my nearly-642 is not a 642, but a Performance Center variant labeled as an M460. (Yes, S&W re-used that model number for an X-frame.)
Moreover, if a gunfight happens, I would rather be armed with a dense, hefty SP101, firing Magnums, than an Airweight .38 Special, so I usually carry the SP101 as my minimum. J-frames are for back-up, or for special occasions and circumstances.
Autos? Eh, a passing fad.
Often, I do indeed carry concealed a P229, because that is what I carry on duty, working for a PD that mandates we carry certain specified .40 double-stack DA autos. When dressed in suitable clothing, a P229 is easy enough to conceal, and comfortable for many hours, but after a certain point, especially if sitting, the SP101 is more comfortable. I have dozed off in a recliner, and napped for hours, while wearing an SP101 in a Milt Sparks PMK. That is simply not feasible when wearing a P229, as it will poke my side if I lean back while sitting.
What if five rounds is not enough? Well, that is why I usually have another SP101, of course.