@Slowboy Good call on staying aware from Vargas. VTTs products & people are trash. You would be better off burning your money.
Yes. The material the studs are made out of matters a good deal as does the size of the stud used, thread engagement, etc. All studs for the n54 are not made equal and not even close. Also in the N54 world people have been getting screwed on head studs since the beginning. People were selling 'upgraded' n54 studs from a Chrysler 2.2L kit iron block re-purposed for the BMW N54 and even though "they fit" the crap 1" thread engagement rips out and lifts the head. Probably worse than stock give the lack of thread engagement. You want/need 1.5'' of thread engagement.
The standard 8740 ARP is a 180,000 psi tensile strength, the ARP 2000 is 220,000 psi tensile strength. The largest ARP offers for the n54 is 11mm:
https://store.vacmotorsports.com/arp-head-stud-kit-bmw-n54-p5393.aspx which are not the ARP 2000 as far as I know, they are the normal 8740 which means 180k tensile strength
I believe Billiam uses 11mm 625+. The 625+ being the big difference. The video below explains the difference rather well:
https://www.autospeed.com/cms/a_113138/article.html <-- Explains the various grades as well
625+ is 280k psi tensile strength or 100k more tensile strength than the standard ARPs!
I know they make 12mm 625+ head studs for the n54 and people have used them successfully. Ghassen used these for instance on one of their builds. Not that I would let Ghassen build my motor or touch my car. The Zeroto60 Australian guy also used 12mm IIRC. The 12mm studs fit the Athena cutring head gasket which is nice.
Stock is M9 or 9mm
9 vs. 12mm = 28.57% difference in size. Almost 30% larger. That is a huge difference in clamping force and holding the head down. 12mm and 625+ is about the best you can get for the n54. Choose once, choose right, like most things in life it is worth doing it right the 1st time, even if it means you have to spend more money up front.
Again, not all 'upgraded' N54 head studs are the same or equal. Size, material, thread engagement, etc. all matter. It is important to understand this when choosing the head studs you want to use in your build.
TL;DR Basically you want 11 or 12mm 625+ studs for your N54
edit:
https://www.spoolstreet.com/threads/to-arp-or-not-to-arp.7971/ <--
@fmorelli this is your thread which is full of good info as well on this subject. There are pictures of at least 6 different head studs for the N54 and you can see they all are somewhat unique in material, design, thread length, cut vs rolled threads, etc.