i have tried jumla and drupal before and they looked a lot more technical, also i could not find enough help about them. So, overall when i compare them, or just in general, when i compare other cms to wordpress, i find the following things, this is just a personal experience/opinion:
spam – on wordpress with akismet/bad-behaviour/recaptcha etc. spam is almost none. while i have faced spam problems on every other cms that i have used.
speed – there are plenty of ways to speed up wordpress, but other cms always lack speed somehow or the other, and i could not find any way to speed them up anyway.
usability – wordpress is easy to use, but then perhaps am so used to it that it looks easy.
features – wordpress has plenty of features, and none other cms can truly match it in features.
plugins and templates – seriously and i guess you would agree too, that wordpress has the most free/paid plugins and templates available. there is a plugin for almost anything that you want to do.
support – so many people use wordpress that they are so friendly, that support is never an issue. just look at this forum, how easily the problems are solved with so many people helping each other. and yes, i had a lot of support issues with other cms and some of those experiences were really horrible.
the list can go on and on…
cheers,