For basic networks, Circon is easy and fast to work with. Much faster the Lonmaker.
Lonmaker has some nice features such as autodiscovery and the ability to use their generic browser, etc...
The CirconBasic language for writing programs in the programmables is a plugin so you can open it up in all three softwares... it's LNS based. They charge a little for it, whereas Distech's programmable language plugin is free. Distech's plugin is the same way... that's why they have plugins. (unlike some OEM's who develop some exclusive software you need just to program)
Also, any one of these softwares can open up a database created in the other... I use LM and NI or NI/VI all the time. I use LM with Circon for most of my stuff.
There are other LNS based softwares... H-well, Newron... I'm sure I'm missing some.
Anyway, if you go LM get a PC with a fast hard drive and packed with processor and RAM.