For a game gun, ghost ring sights. For a defensive firearm, something along the lines of Trijicons, IWI "dot in a bucket" ala Glock, Heinie Straight 8's, etc.
I personally like the Glock "dot in a bucket" sight pattern for speed and ease of use with acceptable accuracy in a speed situation. With practice, they are as accurate as anything on the market. It all depends on how much you train (not primer testing, real training!

).
Ported Glock for defensive use - No @#%(~! Way! Muzzle blast galore. Granted, carefully selecting your loads will minimize this but, I also shoot 9mm from a G17 that produces muzzle flash from a non-ported pistol in broad daylight. Load selection is the key here. If you need the G20C to handle recoil, you need training to master your technique. If there is any doubt left, just look at Glock's own advertising for the "C" pistols!
I am approximately 5'4" and weigh ~160 (which is 20lbs too heavy for me but, I am currently trapped behind a desk with a bad cafeteria and too many vending machines). I
carried a Glock 20 with my
Texas Concealed Carry Permit. Yes it has square edges which make it harder to conceal but, proper holster selection makes this a non-issue. A 1911 or Browning Hi-Power with their more rounded shapes will not outline as easily but, proper holster selection negates this minor advantage.
A G20 is a very flexible firearm. People have been known to buy properly fitted barrels for it so it can shoot 9mm, 40S&W and, 357Sig. With 10mm alone, you go from 40S&W weak loads to hot near 41Mag levels.
Buy a G20 like you buy a hammer. It is a tool. It isn't pretty. It isn't something to brag about to your friends. It is extremely reliable. Is is extremely easy to maintain. I shot a G17 for 18months about 500 rounds a month average and stored it in a bank safety deposit box for six months while I was in West Germany without cleaning it, ever - not even a dunk in a water bucket! When I came back and picked it up, it fired the same as it did when new, no rust, no corrosion of any kind I could find. I stopped counting rounds with this G17 at around 30K. This pistol has been used long and hard and has held up extremely well. How many other pistols will take this sort of abuse without problems?
I prefer the clean single action trigger break of a tuned 1911 or Hi-Power. The single stack mags and slim Hi-Power mag are easy for untrained people to grasp. If the @#^! hits the fan, I will grab a Glock every time. Yea, 15 round mags are expensive these days but, if my life is on the line, I won't really care if the mag cost $10 or $100.