I used to worry more about good runtime performance. Now I prefer to use a language that is easier and faster to use in development.

re: pluses and minuses:

Lisp:

+ better interactive development style; I'll keep a Lisp repla open most of the day. For Ruby, irb is not something that I live in.

+ really great runtime perfromance

- not as many libraries for web frameworks, database, etc.

Ruby:

+ very concise and fun to develop with

+ many great libraries and frameworks

- poor runtime performance