Right now the 2200s are the only cars being replaced, 2400s are still intact as a fleet. When the 5000s first came onto the CTA, they were placed into service on Pink. The Pink line's 2600s then went to Blue, replacing 2200s one pair at a time. Now that Pink is fully equipped with 5000s, the latest deliveries of 5000s are replacing displacing (note, not replacing) 2400s on Green. Those 2400s are now being placed onto the Red line, and the 2600s they're displacing are, one pair at a time, replacing 2200s on the Blue line. Once all the 2200s are gone from the Blue line, then you'll probably start seeing direct replacement of 2400s on Red. Unsure how the Purple line's fleet of 2400s will factor into this.
2200s may be perceivably more reliable than 2400s, but having worked on similar equipment, one thing is true: when stuff fails on cars that old and you need spare parts, GOOD LUCK. Aside from ~2 electrical circuits (one being the automated announcements), nothing on the 2200s is more advanced than a transistor. It's also been relayed to me by more than one CTA employee that 2400s maintained at the Harlem shop on Green are better cars than those on the Purple being maintained at Howard (because the former facility is nowhere near as busy as the latter). Based on personal experience I'd say they're correct - Purple 2400s are absolute dogs, with flat wheels and out of sync propulsion control groups.
That old car might be worth money!