Div.2 has more design and examination for less material (higher allowable stress=less safety coeff.). Some requirements in common but they are brother Codes edited completely different.
Mauro

Please see U-1(d) for details of ASME SEC VIII Div-1.

Regards,

Murtaza

Some key differences...

Div.1 normally up to 3000 psig, Div.2 no pressure limits; Div.1 design factor 3.5, Div.2 design factor 3.0; Div.2 more stringent NDE; Div.2 all full penn welds (I think); Div.1 does not require engineer input, Div.2 requires experienced vessel engineer to stamp user design specfications and manufacturer's design report; Div.1 hydro factor 1.3, Div.2 hydro factor 1.25

There are more in a document I have but I couldn't figure out how to attach.

Please note that Div. 2 was completely re-written in 2007 Edition.
Design Factors have been revised, and many other details. The 3.0 mentioned above are outdated for four years now.

This discussion does not comfort me, as there are many specific details in the Code, both div. 1 and div. 2.
I can only caution the user, designer, manufacturer, and inspector to take some time to read the rules carefully, and then do the job in a professional way. Pressure vessels are dangerous beasts and their construction should not be based on a sloppy answer in an internet forum .
In our experience we see many people doing their job in a professional way. The very rare cases of vessel accidents are supporting this good overall image.

Worrying are the few amateurs playing in this field. Outdated or unavailable Codes and sofware are indications for lack of professionalism.
We see some unsafe designs, some uneductaed engineers, some fabrication violating all known rules of QC and metallurgy, followed by inspectors not inspecting properly. When all these come together, the ground is prepared for another vessel disaster to happen.

DK