Indeed, code reuse, testing, maintainability, etc are harder with the latter pattern. And with the latter you also end up using at least 3 languages in the same files. It's just really awful.
Yes, browser-rendering SPA frameworks are heavyweight, but they give an undeniably-better development experience. And that shows in the quality of the interfaces created through them, assuming your interface requirements are complex enough to justify it. I mean, I'm happy with Hacker News' interface and it's simple, but if I'm building the next Google Calendar, I am not using ajax and server-rendered templates.
Yes, browser-rendering SPA frameworks are heavyweight, but they give an undeniably-better development experience. And that shows in the quality of the interfaces created through them, assuming your interface requirements are complex enough to justify it. I mean, I'm happy with Hacker News' interface and it's simple, but if I'm building the next Google Calendar, I am not using ajax and server-rendered templates.