Is Tojiro or Shun better?
The Shun Classic is noticeably better all around, superior fit and finish, a beautiful Damascus blade, a nicer handle, and lifetime sharpening, and it's the one I'd pick. But the Tojiro DP is a genuinely good knife with the same family of steel at roughly half the price. Choose Tojiro for value or a first Japanese knife, Shun for a buy-once upgrade.
Do Tojiro and Shun use the same steel?
Essentially the same family. The Tojiro DP uses VG-10; the Shun Classic uses VG-MAX, Shun's refined variant of VG-10. Both are hardened to about 60-61 HRC and both take a fine edge. The core steel performance is roughly equivalent, the price difference is in finish, handle, looks, and service, not the cutting steel.
Is the Tojiro DP worth it?
Very much so, especially for a beginner or a budget buyer. It's real VG-10 steel, made in Japan, with a clean grind and a keen edge, widely considered one of the best values in Japanese cutlery. The handle and finish are basic, but the blade is the genuine article.
Why is the Shun so much more expensive?
You're paying for refinement, not better cutting steel: superb fit and finish, a Damascus-clad blade, a polished PakkaWood D-handle, and a lifetime sharpening service. The core steel is comparable to the Tojiro's, the premium is the whole package around the edge.
Which holds an edge longer?
They're very close. Both use VG-10-family steel at 60-61 HRC and hold a keen edge well. Differences in edge retention between them come down more to sharpening and care than to the steel itself.
Can I sharpen these at home?
Both can be sharpened at home if you're comfortable with hard Japanese steel and whetstones, and careful about heat. A coarse pull-through or hot belt will ruin either. If you're not set up for it, the Shun includes lifetime sharpening, and any sharpener who knows Japanese knives can handle the Tojiro.