I want to start from this statement:
On 1966 the US succesfully landed on the moon with a Surveyor class probe.
This family of probe, if compared to today's technology, were almost
"primitive"
(they were the state of the art in those years), but in 3 years US
succesfully reached the goal of
a soft moon landing 5 time on 7 attemps. What I am asking is why, with a
probe that used a '60 technology,
the US had a better success/failure ration than on mars today. Also the
Viking mars lander reached a 2/2 success ratio
using an end '70 technology (and a lot of money).

Now I am assuming that:

Positive point about a MOON landing mission:
+Less gravity than mars
+Less relative velocity between the probe and the target (moon) than with a
mars mission (I am guessing that, but I think that this statement is
correct)
+Less time to reach the moon than mars so less time exposed to the outer
space environment

Negative point about a MOON landing mission:
-You can't use a parachute (no atmosphere)
-You had to use retrorockets to slow down the lander, it's for sure a more
complicated device than a paracute+airbag


Positive point about a MARS landing mission:
+You can use the atmosphere to slow down the lander
+You can use a parachute or a series of parachutes to slow down the lander
+You can use airbags for the last part of the slowdown

Negative point about a MARS landing mission:
-6/7 months esxposed to the space environment
-Greater gravity of mars

So looking at this brief personal analisys it seems simpler to land on mars
than on the moon, if we don't consider the travel phase,
'cause you can land using a simpler and probably safer series of device:
parachute+airbags VS retrorockets, but although
this the first attemp to land on another body (moon) were done with a more
complicated technology (and in the '60) with an higher success/failure ratio
than
recent mars missions that use, from my point of view, a simpler and safer
technology (see the failure of mars polar lander that used retro).

Thanks in advance for your opinion

Alessandro Z. aka [Starline]