If price is an issue be aware that DL is telling investors that they plan to extract additional revenue from their brand’s perceived superiority through higher fares. It doubt it’s going to be over the top but I’d be willing to bet a lot of folks are willing to pay 5-10% extra to fly DL.
I switched a few years ago from UA GS to DL Diamond for reliability reasons. DL often goes weeks or months without a mainline cancellation. Their 2nd generation WIFI is as fast as home (streaming Netflix and HBO) and always works. One downside is that everyone is diamond so upgrades to first are unusual.
Their international network, especially to Asia, sucks and they have be offloading a lot of destinations to KE (which is a miserable airline). Europe is better but is still heavily dependent on KLM/AF.