2x3x4 is brighter and, IMO, has a better diffuse glow. The 1.8mm has a weird heavy concentric glow with heavy falloff on the edges. That said, both are nice, but it you want bright, 2x3x4 is the way to go.
And, for the record, I've used TA PBT, Cherry caps, and others with no issue with 2x3x4. I think it's mainly Imsto that has issues with it.