Probably the Specialized Tarmac SL8, by a small margin. Independent wind-tunnel testing cited by reviewers puts the Tarmac SL8 at roughly 209 W at 45 km/h — within a few watts of dedicated aero bikes like the Cervélo S5. Look does not publish comparable third-party numbers, and the consensus from BikeRadar and Cycling Weekly is that the 795 Blade RS prioritized stiffness over outright aero, claiming a 10% improvement over the previous 795 rather than absolute leadership.

In practice, the difference at sub-35 km/h group-ride speeds is invisible. Both bikes feel fast.

The Specialized Tarmac SL8, by weight. The S-Works comes in around 6.6–6.8 kg in size 56; the Look 795 Blade RS Dura-Ace Di2 is closer to 7.3–7.4 kg in size M. That's roughly a 600–700 g gap — about 1% of system weight for a 70 kg rider, or ~10 seconds on a 30-minute climb.

That said, multiple reviewers (Cyclingnews, Cycling Weekly) note the Look climbs better than its weight suggests thanks to its rigid bottom bracket and steep 74.5° seat tube. It "screams for standing climbs at max heart rate," per Cyclingnews — just don't expect it to match a sub-7 kg Tarmac uphill.

Look 795 Blade RS: 30 mm officially. Stock builds ship with 28 mm Continental GP5000s on Look's R50D carbon wheels (21 mm internal). Reviewers note the relatively narrow internal rim limits how much extra volume you actually feel.

Specialized Tarmac SL8: 32 mm officially, with most builds shipping on 26 mm S-Works Turbo tires that nearly every reviewer recommends swapping for a 28–30 mm option.

Neither is a gravel bike. For chip-seal or rougher, look at a Roubaix or Caledonia.

Specialized: Yes on most builds — Quarq on SRAM Force/Red builds, 4iiii on Shimano builds, even on the $4,699 SL8 Comp.

Look: Only on the SRAM Red AXS spec. Reviewers across Cyclingnews, BikeRadar and Cycling Weekly call out the omission on the Dura-Ace and Ultegra Di2 builds as a hard-to-justify miss at this price point. Plan on $400–$700 extra if you want one factory-installed equivalent.

The Look uses a two-piece Aero Combo bar and stem. Stem length and bar width can be swapped without re-routing hydraulic hoses — a real advantage over fully integrated systems, and one BikeRadar and Cycling Weekly both highlight as a meaningful practicality win.

The Tarmac SL8 Pro and S-Works use the one-piece Roval Rapide cockpit. Adjusting stem length means buying a new unit (~$450) and a partial brake bleed. The Tarmac Expert and Comp use a more conventional two-piece setup with a six-degree integrated stem and alloy bar — friendlier to fit changes.

No. Both frames are wireless/electronic-only, with internal routing designed for Di2 and AXS. If you want Shimano 105 mechanical or Campagnolo cable-shift, you're outside this conversation.

Lower production volume and a more premium build floor. Look's catalog on the 795 Blade RS starts at the $10,700 Shimano Ultegra Di2 build — there is no Tiagra, 105, or Rival entry point. Specialized, by contrast, sells the SL8 Comp at $4,699 with SRAM Rival AXS, the SL8 Expert at $6,499–$6,999, and the SL8 Pro at $8,499 — all on the same FACT 10r frame the higher tiers use.

For a buyer with a budget under ~$10k, the Tarmac is genuinely the only option of the two.

Specialized has a far larger global used market (Pro's Closet, The Pro's Closet, eBay, BikeExchange) which means easier sales but also more inventory pressure. S-Works frames typically depreciate 30–40% in the first three years.

Look is sold in much smaller volume in North America. The 795 Blade RS holds a niche following — listings are rarer, but so are buyers, and the bike is less universally recognized than a Tarmac. Both depreciate fastest in the first year. Buying a one-season-old bike is the cheapest way into either platform.