Is it good to have a - net or + net?

You will get differing opinions on this subject because people have very strong opinions about eating exercise calories back. Based on the way MFP is designed, your net calories should be a positive number close to your initial daily calorie goal. If your daily intake goal is 1400 calories, your net should be close to that by the end of the day. This is because they figure a deficit into your daily goal and allow you to eat back your exercise calories burned.

Again, I offer no opinion on this subject...just advising on what MFP suggests based on their settings.