Diverging views there GSH, which is healthy. Having lived in a lot of variously heated homes and paid plenty of fuel bills I still recommend them. As they do the job perfectly well and you don't need to run them for any longer, the efficiency argument seems specious. In fact, replacing the rads presented the opportunity to re-assess the BTU output per room and we were able to revise downwards. Forgot to say we left the 'modern' rads in the upper bedrooms and bathroom, where immediate heat is preferable.
One longer view of the efficiency aspect may be to ask whether the slimline rads rolling off the production line today will last long enough to make it to a 22nd century salvage yard. Different strokes for different folks, and if you like them you like them.