the only lock which really rises above the others in terms of still being practical and resisting an angle grinder is the new litelok x3.
	
	
		
			
				
			
			
				
				With 5x more angle-grinder resistance than the best performing D-lock, X1 is the ultimate in bike security: lightweight Sold Secure Diamond armoured D Lock.
				
					
						
							 
						
					
					us.litelok.com
				
 
			 
		 
	 
		 
I have an X3 on order.  Estimated 30 day waiting period to make up the production backlog, so we'll see how long it really takes.  I also considered a Hiplok D1000 but its available locking area is small and it costs more.  Tests on the X3 have informally labelled it just as secure as the Hiplok.  There is a D
X1000 Hiplok coming in 2024 but it is only longer, not wider, than the current model and its going to be even more money I am sure.
I lock up outside every day, often in more than one location.  And I just started going to a new bank downtown for my business, where I have to lock on an open street ... around the corner from the front door.
Locking is best done in independent layers.  Usually, I have two.  A big 18mm stainless U lock secures the bike to a rack, and links in a 13mm boron steel noose chain.  The noose chain goes along the frame and noose-ties around the seat tube and back wheel.  So that is Layer 1.  Layer 2 is a 16mm U lock that just locks around the seat tube and rear wheel.  So if someone detaches the bike from the bike rack, they have to get thru the second U lock before they start rolling the bike away. 
For a quick run inside somewhere - for example my PO Box is 20 feet inside of a door, and the bike is parked literally right at the open door behind the post office - I attach a disc brake lock.  A memory cord reminds me its there so I don't try and ride off with it still on.  Bike is not attached to anything, but nobody is riding off with it either.  Recently, since its another 10-second lock to attach, I started using it as a third layer.  But for a quickee, more-serious lockup I could also use the U lock and the disc lock.
I did all three here.  This was at Best Buy.  I take a picture every time I lock up as my insurance (Markel/Velosurance) stipulates I have to have the bike secured to a fixed object for theft coverage to apply.  The Litelok is going to replace the red/black U lock you can see in the pic, I think.