Here is how these two backpacks compare on the numbers. The Focal 58 takes a modest overall edge, led by low weight, but the Alpha AR 55 has its own case.
| Gregory Focal 58 | Arc'teryx Alpha AR 55 | |
|---|---|---|
| GearScore | 66✓ | 64 |
| Capacity | 58 L | 55 L |
| Weight | 2 lb 10 oz✓ | 2 lb 14 oz |
| Rated load | 35 lb | n/s |
| Fabric denier | 100 D | 315 D✓ |
| Price | $270 | $250✓ |
| Type | Backpacking | Backpacking |
| Frame | Internal | Internal |
Highlighted cells mark the better spec: Focal 58 in blue, Alpha AR 55 in amber. A blank spec is never counted as a win. Capacity is shown for context and is not scored, since more volume is a sizing choice rather than better. GearScore is the overall rating (0 to 100); re-weight it on the full backpack comparison. Prices are current MSRP.
The Gregory Focal 58 against the Arc'teryx Alpha AR 55 is a study in priorities. The Focal 58 wins on low weight, and the Alpha AR 55 pushes back on durability and price.
The Focal 58 is 4 oz lighter. The Alpha AR 55 is tougher fabric (315D vs 100D) and $20 cheaper. On the default GearScore the Focal 58 leads 66 to 64.
Pick the Focal 58 if you care most about low weight, which makes it the better call for counting grams on long miles. Pick the Alpha AR 55 if durability and price matter more to you, or you are focused on rough ground and hard use.
The Gregory Focal 58. It is 4 oz lighter than the Alpha AR 55.
The Arc'teryx Alpha AR 55. It is tougher fabric (315D vs 100D) than the Focal 58.
The Gregory Focal 58, 66 to 64 on the default algorithm. You can re-weight the factors to match your trip.
It depends on your priorities. Go with the Focal 58 for low weight, or the Alpha AR 55 for durability. The spec table above shows exactly where each wins.