I've had different experiences replacing the nose seals.
I've replaced 2 seals with the double-lipped Viton versions, and neither leaked. I doubt that the 2nd lip affects whether or not it leaks, because it'* just a dust shield.
I've replaced 1 seal (on a 3rd unit) with the single-lipped Nitrile version, and it didn't leak initially but began leaking after few hundred miles, and still leaks a small amount every few hundred miles, so I keep an eye on it regularly.
I wonder if the leaking might also have to do with the oil level, and the internal pressure at certain temps and RPMs. I suspect this because after I rebuilt the one with the Nitrile seal (but before I installed it) I added another 1/4 bottle even though the oil level was at "the bottom of the threads" before and after adding the extra 1/4 bottle. I haven't added any more oil to this unit since it began leaking a couple of months ago, and the level is still at "the bottom of the threads".
'99 Bonneville SLE, white, 112,000 miles
'02 Park Avenue Ultra, white diamond pearl, 88,000 miles