i use what would be a snugged 1/2 hitch, running bowline, except the snap or 'biner is a resealable/ reusable locking ring (bowline) for rigging. After the half hitch, the working end (snap, bowline) should lace down towards the heavier end, to pull the 2 chokes closed (rather than pulling esp. leading 1/2 hitch open). If the center of balance is opposite, the trail of said lacing it can pull open the leading choke open, if the center of balance is between the 1/2 hitch, running 'biner/snap/bowline; this lacing can slip too. That is on larger stuff where the circumfrence of the spar would sit better against flat steel device (being used at wrong angle of pull); in smaller stuff i drop the hardware (use running bowline rather than snap/'biner) or usually choke with sling.
There are a number of ways that snaps are diffrent than 'biners; others are a 'biner's gate holds back more than 1 link, but a snap has one end in captured eye, snap can have sleeker profile, opening operations are not twist orientated and others mentioned. Though i would always insist on a double locking one.
i don't think the red aluminum ones look cluncky! i thought i would miss the weight for whipping it around anchors and 'boomeranging' back; but haven't had any problem from that. Then Tom's posts disspelling long running rumors about fragility issues of aluminum really helped. So, now i find myself handling it, as it dances around lightly at command, finding real wonder in this light lil'marvel replacing totally it's heavier steel counterpart.
i have had questions (but see no evidence of), excess aluminum wear from an aluminum device riding on a harder steel one; are there any cautions here? Most intense might be Steel CMI pulley eye digging into aluminum linking device (snap or 'biner), it is closest to sharp edge in this position that i have seen,as most other things are rounded steel.