Remember, only a small portion of the blade along the rocker is in contact with the ice at any time. So, all else being equal (and that's a critical qualifier), changing to a slightly shorter blade should not require a change in ROH. If you are happy with a 7/16” ROH, stick with it; don’t intentionally introduce another variable at this time (you have too many uncontrolled variables as is). Hypothetically, increasing the ROH would improve your glide, but cause additional side slipping. So I wouldn’t mess with it for now. Time to check your premises (as Sherlock Holmes would say).
(1) The old boot and the new boot are identical except for the size. The new boot is smaller than the old boot. (By the way, what are the actual sizes?) Are they truly identical? Sometimes manufacturers introduce minor changes without changing the model number. A change in heel pitch or arch support, for example, could affect performance. Check with the manufacturer and skate tech for any unannounced changes. Have the skate tech check for any defects.
(2) The old blade and the new blade are identical except for length. The new blade is shorter than the old blade by 1/4”. (By the way, what are the actual lengths?) Have the skate tech check for any defects, such as warping or misalignment.
(3) The old blade and the new blade were both recently sharpened with identical ROH of 7/16”. But you mention that the longer blade “feels sharper”. It’s hard to get consistent sharpenings, even with a decent skate tech. I usually have to fine-tune myself. Have your skate tech check. By the way, my experience is that changing the ROH by a 1/16” has a significant effect on performance. Detecting a 1/16” change in ROH, however, is difficult. Visual inspection is totally useless. I have a set of precision calibrated machinist’s radius gauges. But even with them, detecting the small change across the narrow width of a figure skate blade is difficult. Really fussy sharpeners use a special instrument outfitted with a dial indicator (expensive and not that common).
(4) The old blade and the new blade are both properly mounted. Have your skate tech check.
Good luck! I hate it whenever I change boots or blades. Always requires a lot of tweaking.