Haltech is overrated IMO. Will my car drive noticeably better with it or make more power? Not really. Nistune is a really impressive product that continues to evolve with a great community. It works great for me.
If, however, I was building a 1000+rwhp rolling lag machine with a powerband that just barely fits into a WOT shift pattern maybe I'd go Haltech while cutting holes into my frame rails or smashing them with a hammer to fit my ridiculously oversized turbo for 1.5l of displacement.