For me, definately 5-10cm. I was 4cm when I arrived at hospital and by then I had had a lot of mild contractions (not really painful, but enough for me to feel it and for it to be distracting and annoying kwim?) My waters also broke and I began much more painful contractions straight away. That happened just after 1am and I think we stuffed around at home for about 30mins before going to hsopital. Got there just before 2am and was told I was 4cm. So dfinately that first half was easier.
The 5-10cm was so much harder - physically , It was very painful (duh) and exhausting. I had been up for about 30hours by that point so all I wanted to do was give birth and go to sleep.
I didnt use a bath - at the time I just didnt want to.. but I did use a shower and it felt quite nice. Dont worry about screaming - I screamed heaps and now I look back on it and i think its really funny !