Actually, even in my time as simutrans head coder (and before my children were born
), I developed the first destination patch (which in principle was the same approach TTDpatch now uses, imho). There are user of both here. (However, the simutrans activities go on at another forum, thus each activites are well hidden from each other.)
About "lagging behind": Simutrans way older, first releases are from 1999. But the direction is very different, with fixed routing of vehicles, destinations, powerline, and a more balanced gameplay with more than 13 different (size) graphic sets with more house than all grfs together ... But forget about this: both games have nice feature, both have different foci, and both communities are motivated in part from features of the other games. Sometimes, like the comic graphics, things are ported either way.
(Open)TTD is way more famous, since it was the first as a commercial game. Thus (Open)TTD fame to Simutrans fame is about 10:1 according to google ranking. However, in certain countries (Brazil, Japan, Czech) Simutrans is 100:1 versus (Open)TTD, while OpenTTD is strongest in britain and germany is a tie. This was maybe due to localisation or active communities there.
I like to look at great maps and see how things flow. A little like a finished model railway, but it is evolving and actually never finished. http://www.simutrans.com