The in office whitening can get the job done fast, but if you have sensitive teeth don't even think about it. The concentration is way higher.
In my professional opinion, the take home trays are a far better value. you can take time off for sensitivity, you keep the trays and can just buy refills for short money.
The most important thing to remember is that you really want to watch your diet while doing a bleaching regimen. I tell patients that anything that would stain a white t-shirt will thwart your results. Red wines, coffees, teas, blueberries...ect.
Also, I really like Arm & Hammer Truly Radiant toothpaste and whitening booster gel, for in between whitening touchups. Works very well.