There's a reason your local gun shop has more pistols in his display case than revolvers. Sales.The day of the revolver is now pretty much at an end with very few exceptions.
Pistols offer more variety in size, weight, calibers, ammunition capacity, actions and manufacturers. Stick with guns made in the United States, Germany, Austria, Italy, Belgium ,Switzerland and the Czech Republic.
Simply, the handgun that best fits your budget, best fits your hand and ability to control recoil. The Sig P-365 is the best selling handgun in America. Chambered in 9mm and .380, this modular design handgun has the best sights, trigger, and magazine capacity in its class. Next down on the list would be the Glock 43X and 48. They are relable, durable and affordable. The S&W Performance Center .380 EZ is an excellent choice as well, especially for the female shooter.
Very little. Replace the too thin slidelock/release with the OEM extended, FBi version. Then replace the sights withTritium night sights like the FBI did when upgrading their STOCK, ISSUE Glock 19M and !7M.