If you're happy with the ec1, stick with an ec1, just get a new one. Running your mouse at 1000hz instead of 500hz should eliminate that skipping. As far as your other options, the sensei and the FK are the same shape essentially, so it'll probably feel a bit small. You're not going to find a mouse with a lod similar to zowie's. Switching from a ec1 to a deathadder will be a nightmare. The DA and ec1 have the same shape, so if you do want one, and want to avoid that pesky synapse, 3.5g is probably your best bet.
I normally ignore this forum, but this thread was at the top so I thought I'd drop in.
I played ESEA Invite TF2 for 3 seasons as a medic
what team / seasons?