whats the difference between each hotend?

Hi I have a question, whats the difference between the different types of hotends? If I was to upgrade the hotend on my Ormerod what would it be? Looking to print eventually in abs, wood filament, and nylon! (Although may well upgrade to a newer printer for some of these!)

Its just working out whats good about the different hotends!

Thanks
Tom

I have a Replikeo Prusa i3 with hot ends. The threaded nozzle into a block of aluminum. The wire mangkement is a concern as they have to pulled up snug to keep them out of the way. My nozzles are 5mm, I believe. Check them out on the Replikeo site. They work but if I have to change out for a size configuration it is a REAL pain. Because I have dual exruders the concern is exact elevation. I adjust one then I have to adjust the other and these are not setup for this.
Someone previoulsy quoted as 'Erector set' type set up. And they are correct. I am looking into J heads next. These seem more modular.