The Short Answer
Buy a road bike if you mainly ride on tarmac, prioritise speed, and like the focused feeling of a racing machine.
Buy a gravel bike if you want one bike that handles everything, roads, towpaths, bridleways, light trails, and bikepacking.
If you're still unsure, buy the gravel bike. It's the more versatile choice, and you can always fit slick tyres for faster road riding. You can't fit knobbly tyres on a road bike.
Key Differences
| Feature | Road Bike | Gravel Bike |
|---|---|---|
| Tyre width | 25-32mm | 35-50mm |
| Geometry | Aggressive, low front end | Relaxed, more upright |
| Speed on tarmac | Faster (by 1-3 km/h at same effort) | Slightly slower but more comfortable |
| Comfort | Depends on frame; can be harsh | Generally more forgiving |
| Off-road capability | None to minimal | Moderate, gravel, towpaths, light trails |
| Mudguard/rack mounts | Sometimes | Almost always |
| Weight | Lighter (7-9 kg typical) | Heavier (8.5-11 kg typical) |
The Case for Road
If you know you'll ride exclusively on tarmac, club rides, sportives, commuting on paved roads, a road bike is more efficient. The narrower tyres, lighter weight, and more aerodynamic position add up. Over a 100km ride, you'll arrive 10-20 minutes earlier on a road bike than a gravel bike, assuming the same fitness.
Road bikes also tend to offer better value at the same price point, because manufacturers can spend the budget on drivetrain and wheels rather than tyre clearance and mount points.