I have a 17X35 vinyl lined oval pool with steps. I am looking to replace the Aquabot robotic cleaner that I've been using for the past 5 or 6 years.The rollers need to be replaced again, as does the cord, so I'd rather just get a new one. I am looking at the Dolphin products. I definitely want a unit with a remote control this time, preferably with top access. Does anyone have recommendations? Any experience with the M5 or Z5?