Straight Grain Advantages?

Soymilk is right on target. There is no advantage whatsoever to a straight grain, except it's appearance, desirable to some. I have a few straight grains, and they look great, but that's far as it goes.

They say straight grain and some of the best looking grain is on the edge of the burl or plateaux. So while the grain itself does nothing for the quality of smoke, being stable or durable, it can might tell you what part of the burl it came from. The best briar for smoking is said to be toward the middle of the burl, ebauchon, because it is more dense. Ebauchon can still yield nice grain just as the plateaux can be 'ugly' or 'boring'. Of course all this could vary depending on the quality of the burl.

Other than appearance, there's no intrinsic advantage to straight grain.

Straight grain high polish is a lovely thing to own. Looks great.
Cost factor can be 1.5 times and often much much more.
'You can't smoke grain'.
A wise refrain.

Tight grain is very important to avoid a foul and soggy tasting smoke. Whether straight, cross or random probably does not matter.

Tight grain is very important to avoid a foul and soggy tasting smoke. Whether straight, cross or random probably does not matter.

Simply aesthetic

Tight grain is very important to avoid a foul and soggy tasting smoke. Whether straight, cross or random probably does not matter.

...FoggyBottom

Click to expand...

+2 FoggyBottom
Grain, especially tight grain, is an indication of the age and respiration channels of the briar. I'd expand on Foggy's point to say that balance of grain is preferred even on a lesser grained pipe or even one that is cut with a lot of wash.
I'll use an example that I believe is close to Foggy's heart. Into the 1960s, Dunhill regularly used chucked replicators where a craftsman oriented the mill cut ebauchon to maximize grain. Their skill is evidenced by many pipes that we've all seen where there's straight grain that runs (sideways) across the shank and up the back and front of the bowl and the sides of the bowl have birdseye.
This balanced grain is possibly why many Dunhill collectors prefer pipes of this vintage to newer ones because the full and balanced grain pattern helps to dissipate heat. I'm not saying that Dunhill made superior pipes in this era, only that when you see this grain pattern or a real straight grain (not a wide flame or variegated wash that some on eBay call Straight Grains) or any pipe with tight and balanced grain pattern it's a better bet to smoke well.