According to my FS, natural FETs give better pregnancy rates. But they are much harder to coordinate as the clinic needs to wait for ovulation, which will often require daily blood tests. If your clinic isn't open on weekends this can be difficult. For this reason, it appears that the regional clinics seem to favour medicated FETs as it gives them more control over when they can transfer rather than being subject to the whims of our bodies.

As for the whether to go for another stim or use that frosty... It can all be a bit of a gamble. I have crap defrosting rates and personally would go for another stim cycle given the choice. However, my FS favoured using all frozen embryos before the next stim (I'm not sure whether this was with everyone or just with me and my bad reactions to stim cycles). It also seems entirely more normal to have much better defrosting rates than I had.

Probably best to discuss it with your FS. From memory you're at a regional clinic that can only operate at set times... Might be best to check out what's possible with your clinic regarding times and factor that into your decision. Good luck!

BW