oldgolfer Some SL sets, like Sterling Irons, have technology to "assist" with distance in the low irons. It sure does work for me.
But really - if your AVERAGE shot is better with a standard length 3i vs single length 3i, bag the standard length one. This isn't the case for most, but it could be for you. For most, they'll be less accurate in terms of dispersion and with center-face contact resulting with an occasional great shot, but a lot of misses. The single length iron would never go as high and as far as the other when struck perfectly, but it's easier to hit more good/great shots with the shorter club.
Totally personal. If I hit my 4i (my lowest SL iron - but loft gapping results in this being a 19° club anyway) lower and shorter than a regular 19° iron, but I could rely on it doing whatever it does consistently, that could still be valuable to me. Better than hoping I hit a decent shot with the regular iron.
Fortunately I do hit it plenty far, so I'm not left wanting for much.