If you're developing a blog add-on, how would you choose between a widget (client side js/flash) and a plugin (server side, powerful) ?<p>A lot of blog widgets have done very well lately - Mybloglog, Addthis, Feedjit, Whos Amung Us, Entrecard ...<p>I struggle to recall a plugin which has done as well (Akismet perhaps).<p>A case in point would be Gravatar (plugin) vs Mybloglog (widget). Gravatar never really took off, Mybloglog is ubiquitous as a sidebar property.
I think you should choose based on what the function of the add-on is.<p>I'm not sure if your options cover this, but some add-ons would be a centralized service (Google Analytics) which you may want to consider as well.