The phone cannot download Flash, or any other plugins, apps, etc. It also cannot open certain sites that require 'pop-ups', does not work with streaming tv/videos or online radio, skype, etc. YouTube does work with the Kin phones, that i can tell you. I believe it uses Javascript (or some other custom plugin microsoft put on) to play videos, and it opens Youtube videos 'through the zune player interface'. I do not know waht you mean by it directs you to download flash, could you be more specific? Do you have 'enable JavaScript' turned on in your browser settings?
As far as certain sites working and others not, that is fully dependant on the site, not the phone. If you are like me, and have never actually had a phone to browse the internet on, it may take a little getting use to which sites have mobile sites, or have fully functioning sites when accessed by a mobile device. It is not like a computer browser, i learned that quickly. It is quick to blame the phone, but most of it is not a Kin phone-related issue, it is a general mobile-internet issue. Only no downloading plugins and apps is phone-related..but if you wanted that, get a smartphone, this is not a smartphone. It costs more money. Whether this is a 'premium' HTML browser or not, that is marketing for you, and premium is a very flexible word. By their definitions, yes, it is a full browser, not just some simple verizon app that allows you to connect to their sites and a select few others.
To answer your question, play61it, yes, both devices can play youtube videos. 3G is verizon's network, and costs money (data plan, or pay-per-use), and Wifi is wireless connection to local networks, but both of them are essentially the same. Mind you, depending on the local WiFi network, if there is a block on a certain site from that network (say, a work or school network), it is still going to be blocked from your phone access, just like it would be from a computer.
