same effort to spin 15s to 14s. just depends on width. 175/65r14 will be easier to get going than a 195/50r15
i personally like the feel of 15s better, less sidewall flex at higher speed = longer slides. tyre pressure comes into play. but the higher tyre pressure you run the quicker you go through tyres.
but i have only been running 14s recently.
but to answer your question not much difference between 14s and 15s, espescially when learning.