I own loads of different types of pegs. My favorite all-rounder are Vargo titanitum nail pegs (not the UL variety). These hold well and can be driven into hard ground which will just piss you off if you try to use any other type of peg (and/or bend your pegs in the process).
For really soft/soggy ground, I like the Toaks Larger V pegs, not the more common smaller variety – if I use a V-peg it’s because I want extra hold and so the larger size really delivers that best. However, the thick nail pegs generally work okay even in soft ground, and if they don’t it’s a less frustrating problem, often remedied by a big rock set on top of each peg or something else creative, than bending up your pegs in hard ground. I find the really thin round pegs like the UL nail pegs and shepherd hook pegs usually do not hold very well, but I find them adequate for guylines most of the time.
My tunnel tents take 16 and 18 pegs fully guyed out, and in practice, I find myself carrying along 4-6 nail pegs for the most critical points (the 4 corners, plus 2 end guylines on the heavier winter tent), a dozen UL shepherd hook pegs (for guylines and around the sides of the footprint), and 4 larger V-pegs (for the corners in soft ground, in which case I’ll still use nail pegs for the end guylines on the heavier tent). In the winter, when the ground is below freezing or will possibly be, I just carry 18 nail pegs and nothing else, no questions asked, because they handle the hard frozen ground best.