TravelLondon tried LED signs a while back I believe on one of their routes and it wasn't well received. People didn't think it was a London bus and avoided using it as they were unsure of the costs and how tickets work, etc. LED sign's are quite messy in my opinion. I mean, sure they do a good enough job but when you take a step back and think for a second, each dot being so easily seen, it really is messy. They are also slightly harder to see from angles, have issues in certain types of light and don't react well to cameras (which isn't exactly a deal breaker, but what ever). They also suffer from issues quite regularly. While they can be treated, I think many issues that develop over prolonged use require the whole unit to be replaced, and way to frequent.
Now, while I am saying these things, they could all happen to roller signs also in different ways, but I still feel LED's have something about them that doesn't feel right. They are too boring and basic. They don't look uniform in the busses and do not suit the London style at all. It would also stop TfL being able to use their signature font as well as they do now. The roller blind is a trademark if you would like to say for London Busses. When fresh, they are a much neater alternative. They also can't be reprogrammed to say something incorrect or inappropriate, which has happened before (while I agree not to regularly). For me LED signs have too much customisation meaning companies get carried around and slap every bit of information they can on there which makes it hard for me to work out tbh. I would be extremely upset if the Rollerblinds were to go, it just removes a large bit of character from the busses. I was even upset when they started making the blinds white, it just didn't feel right to me.