The Salkantay Trek is longer and harder
The Salkantay Trek is twice the distance of the Inca Trail, which is one of the main reasons it's the more challenging trek.
Elevation map of the Inca Trail and Salkantay Trek
You climb about 600 m (2,000 ft) higher on the Salkantay Trek than you do on the Inca Trail.
There's more scenic variety on the Salkantay Trek
You climb higher and closer to the snow line on the Salkantay Trek, while also trekking lower and deeper in the rainforest.
The Inca Trail has more historic ruins
Runcuracay. This circular-shaped ruin is located at 3,800 m (12,500 ft) above sea level and served as a watchtower for the trail during the time of the Inca Empire. Sayacmarca. This well-preserved Inca site features intricate stonework and is believed to have been a religious or ceremonial complex. Phuyupatamarca. Also known as the "Town above the clouds", this site is perched on a mountainside and offers stunning panoramic views. It contains agricultural terraces, baths and residential areas. Wiñay Wayna (see below) . Wiñay Wayna is an impressive complex featuring agricultural terraces, residential areas, and ceremonial structures. It's one of the most impressive ruins on the trail.
Note that because Inca was an unwritten language until the Spanish arrived, many Inca names have variant spellings. Even the name Inca is sometimes spelled Inka.
You don't have to camp on the Salkantay Trek
Your accommodation options are much more varied on the Salkantay Trek.
You can camp with a tour operator just like on the Inca Trail. You can bring your own tent and camp independently. You can stay in hutted campsites (the Sky Domes let you gaze at the stars!). You can stay in hotels. You can do homestays.
If you don't like camping, then you should opt for the Salkantay Trek over the Inca Trail.
You have to join a guided group on the Inca Trail
Porters vs muleteers
Interacting with locals
As with most places one visits, knowing a few local phrases tends to foster goodwill and should help you to get conversations started.
Peak seasons and crowds
The Inca Trail must usually be booked earlier
Note that Inca Trail permits are non-refundable and non-transferrable.
The Salkantay Trek can be done cheaper
Time to choose ...