My only thought is like Dave S. say, the polaris suction line in the wall of the pool is just one more place that could potentially spring a leak some time down the road.
Your friend who went throught two of them may not have had one of the better robots with a proven track record.
Robots have improved drastically in quality in the last few years and continue to do so. I have pretty good feeling that mine is gonna last a few years. But if I only get 3 out of it, I will be happy.
What brand of robots would you recommend? Thanks!