gmail=very simple,feature rich,and gets the job done without making any fuss.HAve you tried accessing your gmail account during fluctuating connection?I have and I love it when it asks me to switch to html version to access it quicker,this is pure magic.
hotmail(M$'s gmail):never tried it much,just once for that cool looking ids
.But I guess gmail is best for me.
Yahoo:kicked out due to never ending loading times and some very annoying features.