Pure adept is very bad. Cyber only will let you make a character who is good at pistols, but not the absolute best, while also being good at other stuff. Cybered adept will let you make a character who is the best at pistols, at the cost of being less good at things that aren't pistols.
The advantage to using natural abilities, rather than a cyberarm of awesome, is that it lets you break the 20 dice cap (if that optional rule is being used) and be better at agility skills that don't just use one limb, like Infiltration.
Take a look at my sig and compare the Ghost (a cyber-only pistol specialist) to the Gunslinger (a cybered adept pistol specialist) for example.