I dislike the word "grade" as applied to high quality steel tubes, as they are all essentially the same "grade" of steel. Based on various treatments, it is possible to make the walls of some steel tubes thinner and stronger, with a lighter frame resulting. But, those thinner, stronger walls are more likely to suffer from crash damage, and many such tubes can NOT be safely realigned after a crash, because the process that makes them light and strong also makes them brittle.

The heavier Reynolds steel tubes made with butted tubes is roughly similar in weight and other qualities to traditional 4130 cro-mo. That sort of steel tube flexes under stress, and if it bends a small amount in a crash, it can be realigned.

Therefore, where durability is the key factory, such as in loaded touring and mountain bikes designed to be REALLY ridden hard, the traditional steel tubing is the "best" tube for the job. If you are a pro, and you are trying to win a time trial (and your bike was free) getting the lightest frame possible is important, even if that frame is a "one crash" frame...heck, you got the bike for free.

So, "best" is relative to the needs of the rider. One of the coolest things about steel tubes for bikes is that a skilled bike maker can match the tubes precisely to the role of a particular bike.

Many of the custom builders "mix and match" different types of Reynolds tubes on a single bike. Schwinn used a "mix and match" of Reynolds tubes on the Paramount, and even used straight gauge for some tubes on the size 62 and 64 models for added stiffness.