Financial products comparison site Rate City has launched a real time ratings system on its website, promising to automatically update product rankings as rates and fees are announced by lenders.Under the new system, mortgage products will be given a rating between one to five points, with a higher score reflecting better value.Rate City's chief executive Paul Marshall said that his company's real time ratings would analyse almost 4,000 products from over 100 lenders and give them a score based on how much the loans cost and how much flexibility they offered.The fascinating aspect of Rate City's new ratings model is that it seems designed to cannibalise the star-ratings model of its sister company, Canstar.Rate City is a joint venture between Canstar's main shareholders and ninemsn. The joint venture also relies on data services provided by Canstar.However, the ties between the two companies don't appear to count for much according to Marshall, who on Tuesday tested the goodwill between the two companies.After announcing Rate City's real time ratings model on Tuesday, Marshall fired a shot across the bows of Canstar and other competitors that their market product rankings were based on judgements that could be up to a year old."It amazes me that every day people are making decisions on their mortgage using out-of-date information, and that banks are paying for an out-of-date badge to put on their site. I frankly find it quite misleading," said Marshall."You wouldn't decide what to wear based on a six-month-old weather report so why would you risk it with one of the biggest decisions of your life?"We update our ratings results as they happen, so if a bank changes their interest rate or product features or introduces a limited time special, the system will tell you instantly how the product stacks up against the pack."