I moved to my 300h from an e-class. To be honest I loved the e-class but it did have its issues. The Merc was extremely comfortable and very nice to drive and returned great economy. Would I buy another Merc? Definitely NOT. A very good car spoiled by poor customer ‘care’ it took 12 months for them to find a faulty sensor and kept telling me there was nothing wrong. Also if I didn’t use the car for a couple of weeks, the battery was flat - they said it was normal. Mercedes don’t care about the customer once they have your money.
is the ES without faults or areas for improvement? No, they could improve it. Comfort isn’t quite as good as the Merc, economy isn’t quite as good (Merc was diesel). Finish is as good on both but where the Lexus wins hands down is in reliability and customer care/support. Customer support get things wrong sometimes but then they admit it and go out of their way to recover the situation.
Am I glad I changed?
I hope this helps you make your mind up or feel more comfortable in your choice.