If your Bow is shooting @ 275 fps and you are using a 375gr.totalwt arrow your ke would be 62.98 lbs...now changing to a lighter arrow { by 25 gr.} and your speed increased by only 10 fps. your ke would also increase to 63.14 lbs. so I would think that it would be in your best interest to change to the lighter arrow...
First, you' re overestimating the gain in speed. In reality, the speed gain would be more like 3-5 fps unless the lighter tip really helped out a severe underspine condition.
this does not sound like a lot but when you are at the breaking point of using mechanical versafixed blade it makes all the differance....Every little bit helps right....
If my KE were marginal for mechanicals, I would not be betting the farm that .16 ft lbs would make a dramatic difference. It' s still going to be marginal.
Change to the lighter weight only if you need to, in the interest of arrow spine or FOC, or both.