I have an older 500 EL/M as well as a 553 ELX. I love them both equally and they obviously both do the same job but to me the 553 ELX feels a lot smoother. I guess age does matter all things beeing equal. Unless you need the "D" i would at least consider the 553 ELX as i believe they can be found quite a bit cheaper than the "D" model. I got mine off ebay for about 250usd but that was without screen and finder. Looks brand new. Either way they are a pleasure to work with regardless of model.