I want people that use xoops to convince me to use xoops. So far it looks like modx is better for seo, but that is just from a few threads I have read.

Seo is very wide definition. It more depends on you and your skills. CMS is just a tool to achive that.

I'm runnig xxx sites on Xoops, and all of them are very nice SE optimized.

So, use Xoops, additional modules and don't worry.

I've used Xoops for over six years now. There were times I looked elsewhere for a solid CMS to replace it but never went through with it. I never really found anything quite like it.

I find Xoops to be simple enough for someone just starting out while robust and customizable enough for an advanced user. It handles high loads very well. My site now sees about 10k per month in unique visitors. Xoops runs just as well as when I first installed it.

Advanced permissions are another favorite of mine and allow me permission or denial of just about anything, module permissions, blocks, etc.

No one can "sell" you on it but yourself. Do a test install, load up some modules and enjoy. It's a solid system that has more than passed the test of time.

I know nobody can sell me on using xoops, but I just want to know what makes it better than others.

I use modx now, but have only used modx. I like cms.

Has anyone moved from modx to xoops?
or compared modx vs xoops?

I've been using xoops for a couple of years (my first posts are from 2004). Through this time I've constantly tried other cms's and frameworks. Right now I'm learning ruby on rails. Not because I need too but because web technology evolves quickly and you need to know what's cutting edge to know where the web is heading.
With that said, I still stick with xoops for several reasons:
-Xoops has been a framework before the term was popular.
-Flexibility. It offers all the flexibility I need through themes and modules.
-Die hard users. I've seen Xoops go through some tough ups and downs and it's still here. With new users experimenting and the old ones still coding a better core and modules. This counts for a LOT if your looking for a long term solution.

Are there better solutions? I'd say there's probably a tailored solution for each level of expertise. If you look around you will see other cms's/ frameworks have solved problems such as SEO in a different/better way then xoops.
In the end a cms counts for 50% of your website. A good part relies on your ability to customize your webpage to it's users. This means delving into php,css and javascript (unless you go the way of ruby on rails).

I've experimented with Xoops, Drupal and Joomla. Have several sites running Xoops (one for 4 years now) and a couple on Joomla.

Xoops is by far the easiest to get up and running with modules. The community is also outstanding for ideas and support. (Joomla forums are so busy it seems like questions drop off the list so fast they often don't get answered.)

Haven't used modx and don't need SEO at all so can't comment on those except that Xoops has focused on and improved SEO significantly with latest version and modules.