That merc you mentioned is a really good SUV.
Test drive the ml500 and x5.
For a family SUV, I'd definitely choose the merc over acura. ml5000 is more refined and composed than x5. I love 4.4i x5's but ml500 is just a touch above it. I have driven both and the ml just felt more smooth and safer. As it is for the family car, definitely the merc. Cant comment on the maintenance on those though.
Range rovers are really amazing cars too but the maintenance is scary on those.