i think you are comparing three glasses of mainstream beer and wondering which one is better.
they are all good choices (assuming 2nd hand hi-flow is in good nick).
they all taste about the same.
they all get the job done.
the biggest issue is that the hi-flow may make a little less power up top (or it may not) but should be pretty line ball down low and mid BUT it should bolt straight on. factory oil, water lines, intake and dump pipe all bolt back on exactly.
the GT3071 and HKS units will have various levels of fiddling around to get it fitted and running potentially adding to the expense.
so if you are happy with 240-250rwkw and save >$1000 then it is hard to argue for spending more money when you will probably spend less than 5% of your time on WOT.
there are heaps of threads on these turbos so it is going to come down to a personal choice.