The short answer
Dodge ended Challenger production after the 2023 model year. The replacement is the Charger Daytona EV (and a future I-6 gas version). Mustang is the only true gas-powered American muscle car still in production. Comparison shifts to new Mustang vs used Challenger. New Mustang has factory warranty + future support; used Challenger has the V8 brute and wider trim options on the used market.
Used Challenger lineup
Used Challenger (LX/LD platform, 2008-2023): V6 (305 hp), R/T (5.7L Hemi, 375 hp), R/T Scat Pack (6.4L 392 Hemi, 485 hp), SRT Hellcat (6.2L supercharged, 717 hp), Hellcat Redeye (797 hp), Demon (840 hp drag spec), SRT Demon 170 (1,025 hp on E85 — last Challenger ever). Wide trim ladder, V8 dominance.
New Mustang lineup
New Mustang (S650, 2024+): EcoBoost (315 hp), GT (5.0L Coyote V8, 480 hp), Dark Horse (500 hp Coyote, track-tuned). 6-speed manual on V8; 10-speed auto on V8 and EcoBoost. No supercharged variant currently (Shelby GT500 was previous-gen; not announced for S650 yet).
Driving feel
Challenger is bigger, heavier, more "muscle car" feel — straight-line dominance, Hellcat soundtrack, wider stance. Mustang is more agile, lighter, more European-style sport coupe feel. Different driving philosophies. Challenger is the drag-strip / cruise / showcase car. Mustang is the road / track car.
Practicality
Challenger has actual rear seats with usable space (relative to other coupes) and a real trunk. Mustang rear seats are tight — kid-sized. If you need real rear seat usability in a coupe, used Challenger has the edge.
Charger Daytona EV vs Mustang Mach-E
For a Mustang vs Dodge EV comparison: Charger Daytona EV (R/T 496 hp, Scat Pack 670 hp) vs Mustang Mach-E (Premium ER 290 hp RWD, GT 480 hp AWD). Mach-E is more refined as a daily; Charger Daytona is louder (Fratzonic synthetic exhaust) and more muscle-car styled.
Future-proofing
New Mustang: active model, factory warranty, parts supply, future generations confirmed. Used Challenger: out of production — parts and dealer support will gradually shrink, especially for SRT/Hellcat-specific components. New Mustang is the lower-risk long-term pick.
How to decide
Pick new Mustang for: factory warranty, lighter / more agile feel, manual V8 still available, future-proof model, Sunrise Ford support. Pick used Challenger for: Hellcat / Demon / Demon 170 V8 brute that Mustang has no current equivalent to, classic muscle car styling, real rear seat usability. Eugenio at Sunrise Ford handles new Mustang.