Visit both at the time of day you will most often be using the facility and see which one has more equipment or amenities available at that time. How much of the equipment is broken or under repair. Price and quality really aren't of value if you have to stand in line to use a piece of equipment.
Ask specific questions about the exact steps to terminate the contract if you find you either aren't making the time to commit or you are frustrated with the conditions at the facility.
Most of the major chains make it rather difficult to terminate.
I followed the exact procedure to terminate to the letter at 24 Hr and it still took 3 months for them to refund all my money. And I was working with the Manager. Planet and LA contracts are very similar.