Physical Dimensions & Thickness: The ASUS ROG Ally X has a horizontal bar chassis measuring 280.2 × 114 × 36.9 mm, while the Valve Steam Deck OLED uses a horizontal bar chassis measuring 298 × 117 × 50 mm. In width, the ASUS ROG Ally X is 17.8 mm (6%) narrower than the Valve Steam Deck OLED. In height, the ASUS ROG Ally X is 3 mm (2.6%) shorter than the Valve Steam Deck OLED. In chassis thickness (depth), the ASUS ROG Ally X is 13.1 mm (26.2%) slimmer than the Valve Steam Deck OLED (36.9 mm vs 50 mm).
Footprint Area & Weight: Calculating surface footprint (width × height), the ASUS ROG Ally X occupies 31,943 mm² (319.4 cm²), compared to 34,866 mm² (348.7 cm²) for the Valve Steam Deck OLED—a footprint difference of 2,923 mm² (8.4%). On the scale, the ASUS ROG Ally X weighs 678g versus 640g for the Valve Steam Deck OLED, representing a 38g (5.9%) weight difference (Valve Steam Deck OLED is lighter).
4:3 vs 16:9 Effective Viewable Screen Size: For classic 4:3 retro games (PS1, SNES, N64, Dreamcast), the ASUS ROG Ally X's 7" (16:9) panel yields a 5.72" effective diagonal (75% active screen area with vertical pillarbox bars on the sides (native 16:9)), while the Valve Steam Deck OLED's 7.4" (16:10) panel yields a 6.54" effective diagonal (83% active screen area with vertical pillarbox bars on the sides (native 16:10)). This gives the Valve Steam Deck OLED a 0.82" larger active 4:3 diagonal (30.6% more active display area). For 16:9 widescreen content (PSP, Switch, streaming), the ASUS ROG Ally X delivers a 7" effective diagonal (100% screen usage) versus 7.2" (90% screen usage) on the Valve Steam Deck OLED, making the Valve Steam Deck OLED larger by 0.2" (+5.8% active 16:9 area).
