I've been travelling all around Spain for the last month and I wouldn't characterize the Renfe/AVE security as anywhere near the TSAs. You basically just put your bags through a machine and get waved through, and I've yet to wait in much of a line.
Yeah, same thing for the Eurostar, it's a much saner security and check-in process. As much as I love flying, I always take the train from London to Paris or between Madrid and Barcelona.
