I like both !!
Although right-handed, I like to use LH multipliers for lure fishing and mackerel feathering..........esp with ABU reels with the thumb release...right hand holds rod and frees spool, left for cranking with no change - over.
With most bottom fishing and heavier gear, RH multipliers. All my Shimano multipliers are RH , but last year I discovered the Avets , and now mostly use these. As they come in LH versions, I've tried these and like them the same as RH....so have a couple of each.
One benefit I found......esp when wrecking with pirks and plastic lures.... it can be very tiring, with a lot of winding during the day. By have a set of left and right on different rods, a swap over every so often, evens out the strain in the muscles !!