Definitly go for best rate of climb (70kts) + max power. As FFF says getting higher quicker is better. Adapting to the changing performance in different condition is all part of the learning process. Think about it before taking off to prepare for it, i.e. solo, have to remember I'll get to circuit height quicker, two up, have to remember to tell x to go on a diet, etc.
although not actually a problem as long as you are within the aircraft's w+b limitations.
If you do the weight and balance correctly on a C152 you will find that getting two up with a reasonable amount of fuel puts you outside the w+b limitations.
D