The gigibot looks like fun - there's also another open frame machine manufacturer in the us with a machine at similiar price. But I think half the build volume.

One thing to bear in mind with the rigidbot. it's got a 0.5mm nozzle. So that's the minimum width bead it will extrude.
If you want to do real fine detail - you'd be better lookig for one that'll use a 0.3 mm or the usual 0.4 mm nozzle.

On the other hand it uses 3mm filament. So you could easily go the other way and use a larger nozzle for faster cruder builds.