Small vs. Full-size HMS Comparison

Hey guys. I’m in the market for a new HMS carabiner. Ideally, I’m looking for an HMS that would be great for all types of climbing, including TR, sport, trad, and alpine. What are the pros and cons of the different sizes.

An easy comparison is the BD RockLock vs the BD Mini Pearabiner.

Bigger carabiners: hold more knots, more strands of rope in anchor, or more other carabiners (e.g. carabiner masterpoint).   May be easier for beginners or big-handed/gloved folk to handle/operate.  Heavier.  Bulkier on rack/harness.  More durable.  Usually bigger cross-section for gigi/reverso/similar.  Usually cheaper.

Smaller carabiners: opposite of above, may be easier for small-handed folk.

big fan of the CAMP nimbus https://www.camp-usa.com/outdoor/product/carabiners/nimbus-lock/ for smaller locker, the photon lock - camp-usa.com/outdoor/produc…

Another nice thing about a big HMS biner is that they work better with a munter hitch. I belayed with a munter using a round stock Petzl Attache and a pretty stiff 9.8mm rope once, it was a bit of a pain. The Attache was almost too small for the munter to flip around, and sometimes the munter will flip onto the spine or the gate. Obviously if you never use a munter on a thick rope it doesn't matter, but just another thing to consider.

Just throwing it out there. I almost exclusively use Petzl Attache carabiners. I find they are the right size for almost everything I do. Great size for a belay device. Great for throwing two opposite and opposed for a toprope anchor. Awesome if you're using a masterpoint carabiner. Overall, it's my favorite locking carabiner.

Another vote for CAMP Nimbus. I like the attaché, but the new ibeam construction wears really quickly.
nimbus is similar to the older style attaché which was my long time favorite 

It will mostly depend on how big your hands are. If you have big hands, small biners will be easy to fumble. If you have small hands, big biners will be cumbersome. It is tempting to buy the really small and light biners, but I would prefer to have one that is easy to handle. I would try a few different ones at a shop or just from your friends to get an idea of what size works best for you.

I will throw in a recommendation for DMM's offerings. Their gates never bind up, and their screwgates are buttery smooth. I always rack a DMM Boa (big HMS which is discontinued but still available). Great for belay and rappel, and use as a big masterpoint biner. The rope bearing surface is partly I-beamed, but still round enough to be low resistance. The Boa has been replaced by the similar,  mid-sized Shadow HMS. While I have not tried the Shadow HMS, the offset-D Shadow screwgate is my go-to general-purpose locker. For me, that is a good size - not too big, not too small. Their small HMS is the Phantom HMS.

A lot of good thoughts have already been covered above.  I carry a Petzl William in my kit most of the time because it is a versatile carabiner.  It's big and a bit on the heavy side so it's only worth carrying if you know how to take advantage of the size.  It's nice for use at belay stations since you can stack a couple of cloves on it and it's really handy for rescue scenarios.  It will also pass a fairly large overhand knot through a munter if you ever have to do that.

I wonder why companies almost never seem to publish the size of the rope bearing surface..?

Here's a size comparison from the new camp HMS biners, the Nimbus (smaller) and the atom (Larger)

I'd also suggest the Rock Exotica Pirate. 

Mammut has a few to choose from in their current offerings.