A drop shot in tennis is a surprise shot and is hard to do well. In squash, a drop shot is a cruciall tool and can be used in an attacking or defensive manner.
You need to be physically fit to play squash and tennis. The constant movement, lunges, and the twists and turns of squash can be more demanding for beginners.
Fitness
Tennis is the harder sport for beginners.
Squash is easier to learn, but hard to get good at.