Rental car vs train from Milan to Locarno in August

Milan to Locarno is less than a 2-hr train ride. Ascona is just 12 minutes further. That makes train travel far less hassle and expense than bothering with renting a car and learning how to drive in Italy. You also would need to pay for a vignette to drive in Switzerland and an International Drivers Permit to drive in Italy.

Just buy a ticket Milano - Ascona on www.sbb.ch. Take the regional train from Milano to Locarno, and the bus from there. All on one ticket. The direct train to Locarno runs every hour. Tickets do not need to be bought in advance, as this is just regional mass transit, but buy it before you board the train.

You can enter the street address of your accommodation in Ascona to have the planner direct you to the correct bus, and bus stop.

Additionally: Is it Milan, or Milan Malpensa Airport that you are starting from? In case your trip starts from the airport just look for Malpensa Aeroporto T1 (or T2) to Ascona on www.sbb.ch

If its just point-to-point travel you're asking about, train is definitely the way to go. Much less hassle.

But if you are planning on taking any side trips enroute, or sightseeing for a few days in the countryside around your destination, you can't beat the freedom of a car.