The bolt on the left is a 1/4 inch button head and may only be about an inch deep which is pretty strong (in good hard rock) if it is not too old or overdriven which can partially pop the head off. The hanger is a newer SMC and is good. The one on right is a 5/16 buttonhead and may only be a tad longer but is a good bit stronger. It too has a newer SMC hanger and I would not worry about this bolt at all as I have placed a lot of them and have removed some too. They are a real pain to get out. The shaft itself is about as strong as a 3/8ths threaded bolt. Don't use them anymore (3/8 stainless now) but not much to be worried about with them if you have to clip one.
I am pretty sure that I saw a bolt on the Last Dihedral whose buttonhead was even bigger than the one on the right-hand of these two. Do you know of any 3/8" compression bolts that were placed in the Southern Sierra?
By the way, the 1/4-inchers produced erratic results in test done by Duane Raleigh. They held between 4,000 lbs and body weight depending upon how well they were drilled. Data
Matt, I believe that I have seen 3/8" buttonheads in the Sierra. I went up a route called 'No Country for Old Men' on the Whitney Portal Buttress and the second pitch was all buttonheads that were slightly larger the 5/16" guys that are in your picture (they have the same SMC hangers on them). I think these bolts were placed circa 1989. They looked pretty good, but I did post a comment on the Whitney Portal page asking folks what they think about the integrity of such bolts. Do you think they are probably okay?