Which is more useful to measure blood sugar, a serum glucose test or a plasma glucose test?

I want to get a blood test that is similar to the one my doctor orders for me during my annual physical, when I have a complete blood workup that measures glucose, potassium, cholesterol, etc. But I only want the glucose portion. Is a serum test or a plasma test the one that a doctor would use, and do they yield different results? From the research I've done, it looks like they both have the same normal range of roughly 65-99. But would taking both tests give me different readings, and which one is more useful?