I am looking for oa good pistol

Question
I am looking for a pistol that is lightweight, durable, and packs a good punch.

Answer
I'm assuming you want to carry this for protection (carrying would be the only reason for a lightweight pistol), so I would add a prior criteria, which would be "reliable."  Any gun you are going to bet your life on must work every time.

"A lot of punch" in a reasonable sized, lightweight package will probably be best achieved by something chambered in .40 S&W.

In my experience, the only gun out there that fits all these criteria is the Glock 27.  I have found other guns to lack the durability in a small .40 (e.g. Kahr), lack reliability (e.g. S&W MP; XD Compact), or be overly large and bulkly (HK USP Compact).