Re: newbie question
Best thing to do is hit them on a course and then check distances with a GPS or laser rangefinder. Range balls are generally very poor quality and won't fly as far as normal balls. Also, it's quite possible one range has signs incorrectly placed, or may be uphill/downhill, or may be affected differently by the wind. If you're hitting the ball decently but hitting it with a 50 yard difference at different ranges, chances are the signs are probably wrong. If you go to a course, the 150 stake (and any other markers, i.e. 100 or 200) will usually be pretty accurate, so you could work with those even if you don't have a rangefinder. So if you found a quiet evening at a course, you could hit a bunch of balls to get a feel for your distances. Or if you can find a (very large) open field you could pace off the distance after hitting some shots.
Also, keep in mind that the distances will vary from round to round and course to course due to wind, elevation, softness/firmness of the course, etc.