Those details don't need to be BIG to see them, but you must have enough magnification and resolution to be able to discern details. The aperture of the telescope determines how much resolution can theoretically be acheived at 13X per inch. Generally longer f ratios are better for bringing out details, but larger aperture and quality optics will produce real results. The biggest advantage of longer f ratios is that you are more likely to have better optics for the same price, since they have more generous tolerances. Small disturbances in the seeing will not degrade the image as easily.
Collimation is another important consideration.
How well your optics are aligned makes all the difference when you are trying to pick out details. This is one factor that you have some control over, since adjusting collimation in most scopes is a relatively easy. Block the glare of sunset with a tree or structure to spot the planet early while it's still light for the best view. This is a sign of irregular cloud cover. Mars' disc is very small, due to its current distance from us.