Go with the Barlow but get one of the Apochromatic 2X. Meade makes one that is excellent. If the scope you are using is a f4.5 DOB, you will find the Barlow a real pleasure to use. Most eyepieces don't work that well at f4.5 and faster so the narrower light cone from the Barlow allows the eyepiece to give much sharper images edge to edge. There is an improvment in eye relief too. Then there is always the "double the number of eyepieces" that you get with the Barlow. If you want to compare, try a 6mm eyepiece and compare it to a 12mm + Barlow. The Barlow will win hands down every time.

Jarvis Krumbein,