Glock 26 vs. Ruger SP101

Sight Radius

This one isn't even close.  G26 by a mile.  With such small guns, 1.5 inches of extra sight radius makes a HUGE difference in accuracy.

Size

This category is really a draw.  They're both about the same size, and despite their different shapes, I can't see how one is noticeably easier to carry.  I've carried both in numerous ways, and they're about the same.

Barrel length

For some reason, semi auto barrels are measured differently from revolver barrels.  With a semi, you measure from the back of the chamber all the way to the muzzle.  With a revolver, you only measure from the forcing cone to the end of the barrel.  If we're doing an apples to apples comparison of these two barrels, you can see that they're pretty much the same length.  Or at least the bullet travels through the same length of rifling for each gun.

Capacity

The Glock with the factory magazines holds 10 rounds, and with a +2 baseplate (cheap and easily installed) the round count goes up to 12.  The Ruger holds only 5 rounds.  The issue of capacity gets even more lopsided when you consider that the Glock can accept a 17 round magazine (or even a 33 round magazine, though that's not really practical for concealed carry).  Essentially, the Glock is a very fast reload away from being topped up with 17 rounds, and the Ruger is a slower reload away from having an additional five rounds.   

Some debate the importance or wisdom of doing tactical reloads (where you reload the gun before it runs empty, and hopefully retain the original magazine with whatever rounds are still in it).  However, with an auto tactical reloads are at least feasible.  With a revolver tactical reloads, while possible, are probably ill advised.  

Training

Training considerations come down to how much you can afford to train, how painstaking it is to maintain your weapon after training, and how enjoyable it is to train.

Cleaning

A lot of people don't even clean their Glocks.  While this is the worst idea of all time (I clean every gun after every range visit), a lot of those people still go years without a malfunction.  If/when one does get around to cleaning his Glock, it's pretty easy, and even the dirtiest Glocks take less than 20 minutes to clean.  Even if you need to replace some springs, you're still not looking at more than 30 minutes worth of work to make the thing like new.

Revolvers, on the other hand, take considerably longer.  Cleaning each one of those chambers is like cleaning a completely different barrel.  If you're the type of person who dreads cleaning his gun, then the prospect of scrubbing out 5 chambers and a barrel will probably influence how often you train with this gun.  And training with a double action revolver trigger and a tiny sight radius takes considerable time.  The net effect is that, unless you really enjoy gun cleaning, you're not going to have the training time, and you're not going to be as prepared as you would be with something low maintenance like a Glock.  

Comfort

Simply put, shooting full power .357 magnum loads out of this thing is not comfortable.  Even if you're a reasonably experienced shooter, it's pretty easy to develop a flinch when firing this little Ruger hand cannon.  A lot of people realize just how difficult it is to be accurate with a snub nose revolver firing full power cartridges, so they practice with .38 special target ammo, and carry .38 special +P.  I think this is a pretty good solution, with one concern.  Is .38 special +P really any better than 9mm +P?  Does it make sense to carry only five rounds in the gun if they're not big, powerful rounds?

The G26 isn't as easy to shoot as a full size pistol, and there is no way it is as comfortable to shoot as the SP101 shooting .38 special.  A lot of people complain about their pinky finger hanging off the frame, and that the bump on the back of the grip is uncomfortable in the palm of their hand.  Both of these complaints are very valid.  However, shooting defensive loads out the G26 is far and away more comfortable (and more accurate) than shooting .357 Magnum out of the SP101.  

Ammo $

Defensive ammunition for both guns runs about the same - currently about $1 per round.  However, for training ammunition, the 9mm has a huge advantage over the .38 special.  Boxes of 50 9mm target rounds tend to run from $10 to $15.  .38 special rounds run about $20 in the places I shop.  Because I can afford to buy more ammunition, I can train more with the Glock, and that should be a key consideration for anyone.  

Dynamic shooting results

Ten rounds of defensive ammo from the Glock at 7 yards fired as fast as I could get the sights back on target.  I think those would qualify as A zone hits.

Same thing with the SP101.  This was five rounds of ..357 magnum.  Definitely not all A zone hits, though they do hit pretty hard.  The recoil on this puppy is fierce!

Round 2 with the Glock.  I skipped round 2 with the SP101 because the recoil started to bother my wrist, and I still wanted to shoot the Les Baer a bit.

For the next drill, I started with two targets spaced on different stands about 4 feet apart.  I started with my left forearm touching the target on the right, with the gun at low ready.  On the buzzer I backed up as fast as I could, while putting one round on the first target, then two on the second, then in this instance I put two more on the first target and two more on the second.  After 7 rounds I still had 3 left in the magazine!  If I had loaded 10+1 it would have been 4.  The first target is above, the second target is below.

Here I tried a version of the same thing with the SP101.  

One round on the first target, then two on the second, then one on the first.  Usually the drill would end here, but I put on more on the second target just for fun.  

Conclusion

I think both of these pistols have their place in a good carry set-up.  But, except for the incredible stopping power of one .357 magnum round, and the limited advantages offered by a revolver over a semi, the Glock 26 is without a doubt the better defensive pistol for most carry needs.  Will you be undergunned by carrying the Ruger SP101?  Not if five rounds is all it takes to stop the fight, but if it takes more than that you better be awesome at reloading a revolver, or have a backup gun somewhere near by.