Calk or silicone?

[MDSA]

Hello - relatively amateur DIY-we here. I’ve been redoing some indoor windows that have broken plaster, gaping holes and mouldy sealant. Ive filled holes with foam and pollyfillered over everything and now need to redo all sealant. I’ve read about how some people recommend silicone sealant rather than decorators calk and visa versa.  Wondering what everyone here would recommend? 

[larry]

Single glazing? Wooden frames? 

[MDSA]

Hi, double glazing and frames are UPVC