Sleeve-joined vs welded rims

want to grab some cheap 29er rims for a SS build for summer (one can but dream 🙂 ) and see these two DT rims, one of which seems competitively priced (everything else except Sun is so expensive these days).

DT 7.1D £47

DT X470 £30

It apears that the X470 is 470g but sleeve joined, where as the 7.1D is 540g and welded. What are the relative merits etc of the two joining techniques? Do they themselves create the weight differential or is that just a function of the slightly different profiles?
cheers