Direct answer
Neither layout is universally better: 5.1.4 prioritizes a more complete overhead field, while 7.1.2 adds rear-surround separation at listener level. In a shorter room with one primary row, four correctly placed height speakers may create a more convincing Atmos bubble than two height speakers plus rear surrounds. In a longer room with space behind the seats, 7.x listener-level coverage may be valuable. The processor, amplification, doorways, seat positions, and upgrade path can decide the issue.
If wiring is accessible, a practical strategy is to pre-wire for 7.1.4 or beyond and commission the channel count that fits the current budget. That preserves options without forcing extra speakers into poor locations. Dolby's official setup diagrams show the intended relationships; the room plan determines which compromise is more defensible.
Sources and technical references
Use the organizations responsible for a product, platform or standard to confirm current specifications and compatibility.
How this answer was prepared
Camelback Smart Homes publishes this FAQ library for homeowners, design professionals, builders and property teams comparing integrated technology. Answers begin with the practical conclusion, then explain the factors that can change it.
Limitations: This is general educational information, not a site-specific design, quote, code determination or compatibility guarantee. Final requirements depend on the property, construction, infrastructure, equipment versions and project goals.