[bluGill]

That depends on how much atmosphere. Mars has enough atmosphere to be annoying, but not really enough to be useful. Winds can throw you off target, but you can't use a parachute for a soft landing.

[stevage]

That's not true. Many (most?) Mars missions with Landers have used parachutes, though they are not sufficient for a true soft landing.

I'm not an expert but I think landing on Mars with no atmosphere would be harder, because you'd need so much more fuel for a controlled descent.