I use C4 bc it's as cheap as they come in Canadian stores and I don't have to order it online. The point is, both profiles are not amazing, 2 scoops, 1 scoop, it's all just flavoured caffeine with some pump & tingle (the Nitrates in C4 actually give me more pump than anything other than HV for some strange reason) and other nonsenseio garbagio.The labels of c4 I was able to pull up aren't even close to two scoops of modern pre.
But I also work out fasted so carbs are meh
Neuro at the very least has some interesting new additions (Zembrin, Teacrine, not bad doses of Noots at 2 scoops) which make it worth my while, whereas Modern Pre just has Citrulline Malate(who doesn't nowadays) and Cognizin. Everything else is not needed.
Price would determine what I would buy. If it costs more than C4, I would rather just spend that money on a better pre altogether, not something marginally better. Also I never have and never will buy USPLabs so there is that.