Bolt threads, which method?

I've come across some contradicting statements on the matter and I was wondering if the engineers among you could shed some light on the matter: which is better, a cut thread or a rolled thread? By better I mean, which would you choose to hold together engine internals spinning at several thousands revolutions per minute? Answers on a postcard...
Or, you know, in the comments.

Oh snap!

Well folks, a chain is only as strong as its weakest link:

It's no surprise that even a brand new chain couldn't cope with the raw, brutal power of the Matchless: 18.5 bhp is nothing to trifle with kids!

No rush...

...and no point rushing with the weather we've been having lately, but still, is this about time or what?!

These are all the bits I got back from the sandblasting guy: I have to say, I was pleasantly surprised by the guy, who I think is a bit nuts, in a good way. Yes it took a while, but like I said we've had some crappy weather, the dreaded holidays and above all I did tell him to take his time with it anyway.
The cost was very reasonable, considering it included pick-up and delivery, so I'll definitely be using them again in the future.
Over time both cylinder and head will take on a nice dull patina and look even better.
The more keen eyed observers amongst you will have noticed there are two cylinder heads here. Since I'm not building a twin-engined salt lake streamliner (wouldn't that be fun though?), what are the extra bits for? I'll put together a faux-engine, to display in my living room, so expect photos of that too, some day.