I started shooting recreational skeet as a teen with my Dad's 28 gauge side by side that he grew up with. I did ok as a newby.
After being gainfully employed for a number of years, I took up skeet again, first with a Winchester Model 12 and then a Citori field grade. I'd drag out the old 28 gauge side by side once in a while and shoot about the same as with the other guns once I remembered to change triggers on doubles.
But bottom line, as I progressed in skeet along with a skeet grade Citori, it was not as easy to transition back to the side by side.
I've never shot a semi-auto at skeet. I do have a Beretta A400 Smurf gun that has not had a round through it yet. Some day, I'll give it a try.
P.S., I took my first pheasant with Dad's 28 gauge. A crossing shot with a lucky pellet to the head. I guess one always remembers their first success on the hunting field.