Slow Motion 50p / 60p to 25fps

[ROCKMORE]

I've been shooting slow motion tests mostly at 50p because I'm in pal and slow them down 50% on a 25fps timeline in CS4. Today I shot some tests at 60p NTSC and converted them slowed to 40% on the same timeline. I removed the frame blend in all cases. Everything seem to work well.
The 50p transferred at 50% is an even number which makes sense but, the 60p to 25 is not.
The 60p to 25 may be degraded to some degree even thought it looks quite good. I suspect I may be better off sacrificing the extra 20% slower motion for sharper final result.
Anyone have a technical explanation to what extent my final 60p to 25fps image may suffer over 50p to 25fps.
Thanks

 

[haircut]

Make a copy of your clip in Finder. Open up Cinema Tools and open that duplicate clip. Under the bottom right of the clip image, click the Conform button. Change your framerate to 24.00 or 25.00 and let it do it's thing. No more changing clip speed in FCP!

Here's a post I wrote explaining the technical differences between the two approaches. Hope it helps!