Hi Chedex12, and welcome to AF
If the feel and handling of the phone are important, the best advice I can give is to go to a shop and try them yourself. I also have small hands, and for me the One feels better (the tapered back is more comfortable, and it's slightly less far to stretch my thumb to reach across the screen). But that's my hands, not yours - you might find less difference, or you might find both too big to be comfortable. The only way to know what feels good to you
is to try them yourself.
Both should be powerful enough to multitask, and both have the same RAM. I'd not personally be concerned there.
As for the camera, if you want to crop part of the image, and are shooting in daylight then the S4's pixel count will give you more detail to work with (the One will win in low light, but that's not your priority). If you want to view the pictures on the screen or on a computer then either should be fine - remember that the One's 4.3 Mpixels are still twice as many as a 1080p screen contains. The One has a wider-angle camera than the S4 and a 16:9 ratio rather than 4:3 - which you prefer is personal, and may depend on what type of thing you shoot.
The One has better speakers, I've never used either with headphones so can't really comment there.
The screens are both good, but different. Which you'll prefer is a matter of personal taste.
If you store a lot of media the S4 has sd card expansion, but less internal memory (unless you can find the 32GB version, which depends on where you are/what carrier). You can't use the sd card for apps.
I honestly can't say which would be better for you. Both are good, but different. But at the risk of repetition, I think the most important thing is to go see them both yourself and see whether you simply like one better than the other.