Both are grid system from the same developer. Jeet is for Stylus and Lost is for PostCSS (I think Lost started as Stylus package but then changed).
What are the differences?
Which one is better for Meteor?
Main difference is that you need Stylus or PostCSS 
Both are really cool. Jeet seems not to be maintained anymore, but maybe I’m wrong.
If you want to use Lost with Meteor I’ve created a small tutorial here: https://github.com/peterramsing/lost/wiki/Installation#meteor
Well, usually people have both 
but Jeet does seem out-of-date. What about your s-grid?
yeah, I use it when I work with Stylus. sGrid is a really small tool, only basic functionality It is very similar to Jeet grid, but based on Flexbox. When you work with Flexbox you need to be careful, especially in IE11 If you want to read about it more I have some links to articles in the readme file: https://atmospherejs.com/juliancwirko/s-grid
Will definitely do. Thanks!