Money down on investment property is better to pay 20% or 30%?

[Calistro J. Garza]

In the process of purchasing an investment property, going with a conventional loan.

My question is,

Lender has me at 5% interest with 20% down puts me at 18k

Lender will do 4.3% interest with 30% down puts me at 27k

What is the right approach? Or should I ask to buy down points?