Mlox only does it if somebody codes the size of the esp/esm into the Mlox DB and the DB gets released, which could be months in-between.
An on-demand lookup would be substantially improved.
Thing is, mlox is going to get a autoupdate feature and a wiki site for modders to create rules.
(It COULD already be making the autoupdate part of it, it's easy since the rule file is in google code, that allows http connections to the svn repository).
You don't actually have to wait for releases of the rule file to update you know.
This link:
http://mlox.googlecode.com/svn/trunk/data/mlox_base.txt
Should always be to the last file in the repository.
The disadvantage of the other method is that there will be literally thousands or even hundred of thousands people hitting your site and through it, hitting the Modding repositories site for searches of mod updates whenever wrye starts up. You could make it better by making the user check for the updates himself, but that loses timeliness.
The advantage is that indeed (and if you can parse the version string ok), you'd get a warning of a new version as soon as the modders uploaded a new version.
They're both still pull models, instead of a push models, and that is "bad" (but still the simplest way), for query reason above. The large difference is that, in one, you query the mlox rule file (and can use the http protocol "last-modified" header to give up if nothing changed. In the other you start searches in a lot of sites ( i think it's the way ES Search works, if i'm mistaken, disregard the last 3 paragraphs of the post).