The best set, and used by most pro gunsmiths is the Brownell's Magna-Tip set.
These are the best quality, they offer more sizes than anyone else, and Brownell's replace broken bits for free.
All you have to do is email them.
The quality of metal and workmanship is top of the line, the range of sizes will fit right at 99.999% of all screws without alterations.
I recommend the Law Enforcement size handles.
The big handle is too big for good control on most applications, and the stubby handle is just too short for good control:
The Dillon sets are OK. Mine has lasted for probably 15 yrs now and the only real issue with it is that I've lost some number of the bits over the years and the too many moves in the meantime. The Chapman set is great. I've had that one for probably 30 yrs or more and same issue as the Dillon, I and the people I've let use the set have lost too many of the bits over the years. If you're in a hurry to get some screwdrivers that fit your screws, try Northern Tool. I bought a pile of new screwdrivers down there a few months back, not intending them to be for my guns, just stocking a new shop, but lo and behold if some of them aren't the perfect fit for most used sizes like 1911 grip screws. So some of them wound up in a tool holder over my bench and haven't scarred up a screw head yet. The main thing is just to make sure that the screwdriver you're using fits in the screwhead with no wiggle, otherwise you're likely to scuff up the screwhead and even those of us who regard the gun as a tool and don't mind normal wear marks on our guns don't like nasty looking screw heads on our prized possessions.
In addition to the Brownell's set, you might want to pick up a little Husky HD-74501S screwdriver, it comes with 4 different combo phillips/SAE bits that store in the handle, from small to very small - works great for eyeglass repair also. I've had mine for years and it's my go-to screwdriver.
1 Of the best investments I've made was a Wheeler Engineering set. I believe it's 71 pieces. LOTS of straight bits, allen bits, torx bits, and phillips bits. Includes 2 handles. I think it was $59.00. I've never met a screw or scope mount/ring I couldn't use these for.
I didn't know the "Chapman" set was so well-known or highly revered!
My Chapman set is 34 years old;still in the red,fake-leather box. I've only "misplaced"(it'll show up sometime) one tip which was only a phillips-head anyway.
I did buy a set of red-handled, "Bonanza" (Fairbault,Minn.) screwdrivers for some reason;but,have never really needed them in addition to my old Chapman set.
Yes I know, I am not from the school of BFH. That's how I broke my Chapman bits using the hand ratchet and handle to remove a stubborn screw. I broke the bit but didn't mess up the screw head. Some of the old gun that my friends bring me to clean or fix are in really sad shape, and I charge extra for the extra effort. Most of the stuff are basket cases and are a challenge to say the least.
I have a 25 year old Chapman (red fake leather box) set myself, but it doesn't have Torx. I started to buy three bits for about $1.95 each plus shipping, but saw the Pachmayr set at Midway for $10.. Got it too.. Ron