I am in pretty similar situation in that i have had an HTC Desire for just over two years and the mangament of space has become a real pain. I guess i am semi techie but i just can't be bothered to go down the rooting path where i could seriously bugger it up.
At first glance the HTC One S looked the perfect replacement. Not too big and construction wise a lot more robust and quality feeling case as opposed to the oversized and plasticy Samsung S3. However, i was gutted to hear about low onboard memory, no removable battery and no ability to expand with SD card.
I really think HTC dropped the ball on this one when trying to compete against Samsung. Despite my reservations about S3 size and construction quality it just might get my vote because i can load on all my music and simply pop in a spare battery when on the move.