the mod. 10 S&W's are good old guns , not sure what guns are the service and service 357 possibly S&W ! 6 shot guns
the SP101 - a real good choice , a 5 shot with a thinner profile . and strong built ! and stainless steel ! a bit heavy for pocket carry in summer but workable , for pocket carry i like a S&W mod. 38 airweight ! the SP101 is easier to shoot well ! and also can shoot 357 mag. if needed ! some feel a 3 inch bbl is better than a 2 , with the SP101 i really don't see much difference to be honest ! the 2 is far easier to carry IMHO !