A local train isn't as comfortable as an express.

Literal

Local-train [topic-は] express [as much as-ほど] comfortable not.

~ほど~ない is the standard 'not as X as Y' comparison pattern. 普通電車 = 'local train' (stops at every station). 急行 = 'express.' 快適 = 'comfortable' — a na-adjective.