Weapons will exhibit a preference for one or more loads. The only way to find out is to shoot as many different types/loads as you can afford.
Micro
You will have to tell us what you want to use it for.
Best is rather poorly defined- best for what? In general, the Ruger Mk II and MK III psitols are accurate, reliable, and good shooters, but so is the Browning Buckmark. There are also fans of High Standard, Colt, and S&W.
The Browning medalist was the best by far.If you can find one,these were made from 1959-1974.
Best left to a gunsmith
Neither.
It sounds like you need repairs done to a pistol. Recommend contacting the Browning Service Dept. at the link below. They will guide you as to the best way to get your gun repaired.
This is best left to a trained gunsmith.
Best left to a gunsmith.
Best to ask a gunsmith for assistance.
All weapons exhibit a preference for one or more brands and projectile weights. You will have to buy as much as you can and shoot to get the answer for YOUR weapon.
At a gun shop or gun show. <><><><> Additional- FIE was an importer of mid to low quality firearms, and is long out of business. Despite the name, none of their .25 autos would really be a "best pistol". Walther, Browning and Colt did make good quality .25 autos.