I'm surprised other people are giving you concrete answers as it is impossible to say.

How much have you invested in building the current ROR based system?

Are the developers happy to code with both or are they simply steering you towards the technology they know?

Magento is a great platform. Extensions are a double edged sword, they can be very good and save a lot of effort. Likewise there are some terrible extensions out there. The cumulative effect of adding lots of extensions can be really bad as well.

Ultimately, you are likely to get what you pay for, no matter which platform you go with.