You can email books to your Kindle from Calibre so that another plus for the kindle so if you convert an epub to mobi and send it over email it really takes the sting out of being locked to Amazon store
But your list of pros and cons are good it really depends on your wants and needs I ordered a K3 as I didn't think the 650 was worth the £199 price tag in the UK and the K3 wifi is only £109 here
happy deciding