Either shooting style is good. Two-handed styles have become more popular as double action became the standard and the effective range of pistols increased. It used to be even the military taught people to shoot with only one hand (sometimes called "military style" or "point" shooting). You presented your shoulder to the target, extended your arm straight until the top of the gun was at eye level, and fired. This style allows for quicker acquisiton, presents less of a target profile, and feels more natural. Obviously you're going to be more stable with two hands though. Kind of oddly, now when we teach people to shoot one-handed due to an injury or whatnot, we have them more or less maintain the two-handed stance instead of teaching them the older style.