What are the reasons institutional investors prefer SOL over others?

Solana is by far the sole number one token in terms of speed and bandwidth. And with Firedancer this will increase tenfold. Big companies that want to actually use blockchain technology and scale their web 2 applications are just looking for what works best. VISA recently announced a partnership for example.

All in all some of it is probably just speculation. Solana is one of the few top 10 coins that has a great upside potential since it was oversold and there is great room for improvement market cap wise.