For me thats a pretty tough choice. I own a variety of firearms and in my mind they all have a specific role they play well. If I could only have one and thats knowing what I know, it would be between a Sig P229 in 9mm or my SP101 in .357mag. Around here ammo for either is pretty much the same price.
I guess it would depend on where I live and what percieved threat I could have. If the threat is high (bad neighborhood) I would go with the P229 for the capacity, low threat would be the SP101, low capapcity, high power could also use to hunt if needed.
Either gun will last a lifetime with proper care. Good luck.
BTW I had a few anti-gun folks change their way with a trip to the range and let them shoot, they usually enjoy it very much.
Nov 2, 2011 sent form 4, SS Sparrow. Arrived May 29, 2012.
Jan 30, 2012 sent form 1 for SBR. Arrived July 12, 2012
Jan 22, 2013 Sent form 4, 762-SDN-6. Arrived Sept 13, 2013