The delta-sigma is conceptually very similar and gets you most of the way there for DC performance, but can be used for sample rates in excess of 100 kSamp/s. Multi-slopes also need large passive values that make an integrated solution impossible. Keysight will still sell you their 3458A.
Also, the AD7177-2 exists. That might be evidence enough for delta-sigma's victory.
Also, the AD7177-2 exists. That might be evidence enough for delta-sigma's victory.