the biggest difference is that mixcloud is streaming only, the listener cannot download anything. but mixcloud is free and now has unlimited uploads. they request you do a full tracklist but dont check this as long as you put something in the tracklist which could just be 'unknown' - part of this is for licensing but also partly so their system can identify songs to provide the link for people to buy them. if you have well known songs in your mix but dont label them the chances are the system itself will identify and complete the tracklist for you which is a bit 'big brother'.
soundcloud you get 2 hours content upload for free and they also have EURO 25 option to upload 4 hours worth of content so if you only want to have a few mixes at any time then that is fine. you also get some limited stats of where your listeners are. soundcloud originally was more targeted to producers putting up individual tracks but it now has lots of mixes and live recordings too. in terms of actual use they are pretty similar but overall i think soundcloud is better designed with improved functionality (eg leaving comments, following others, growing your listener base etc). just set up a basic free account and compare how you get on with both of them in tertms of listens and promotion etc.
i recommend doing a tracklist though at the time of upload for anything as it is unlikely you will ever get round to it otherwise and its really easy to forget what a song is if someone asks you later on.. also if you are making mixes available for download you should at least give some recognition to who made the tune so people can buy it if they want to.
i used to use podomatic, then moved to mixcloud and now i mainly use soundcloud, but i will be changing the mixes every month so they are not just sitting there for years. although based on my own profile i think downloading mixes is not something that many people do these days - it seems like only about 10% of my listeners actually download the mix so the landscape has definitley shifted in that regard and i think this is a generational thing - first step was people didnt want to own the actual music physically, but now they dont even want to have it semi-physically (as mp3), all they want to do is 'favourite' or 'like' it so they can find it again next time they are online.
i did put a few things on talawa but it just never seems to load properly for me no matter which browser i use so dont really use it anymore but that will be a core roots reggae audience who really know their stuff so def worth making a profile and putting stuff on there to make industry or soundsystem connections.
then yes on here you put links to mixes in the audio board