The 14 year old door steel faced outside doors on our house are reaching the end of their life which I understand is the normal life expectancy for this type of door. I don't fancy UPVC rubbish so it boils down to a choice between composite or hardwood.

I just replaced mine with a natural oak one off ebay
Treated it with a good uv resistant oil - looks amazing

Wood wins on looks and feel for me.

Problem with wood is the swelling you get over time and maintenance. That said, uPVC doors have a certain 'style' that screams "old lady" about them, so I'd take the maintenance on a timber door any day.

We have a steel door with foam core which has been fine in most ways, only real issue is that it radiates cold in the winter like you wouldn't believe, and the opposite when the strong sun is on it in summer (like now). It would be much better if it was the other way around!

I'd say go for whichever suits your house the best. At the risk of teaching you're granny to suck eggs. If hardwood, seal (at least two coats) the end grain before the final fit, especially the bottom as it's difficult to do once hung. When you buy a door, sight down it to make sure it's not twisted. The bad thing about fitting a wooden door is usually the frames knackered.