The option you get is
1. yellow Honda Civic Type-R (2000)
2. red Ford Mustang Foxbody (1990)
3. white Subaru BRZ Premium (2014)
The answer of course "hachiroku" :v

Subaru BRZ Premium (2014). not only this car have great performance at stock (you can beat two tutorial races very easy using this car, as long you not crash). its also have higher price sell than other two.

here selling price for all starter cars,
1. Honda Civic Type-R (2000) = $10,530
2. Ford Mustang Foxbody (1990) = $15,600
3. Subaru BRZ Premium (2014) = $17,810

so by selling price Subaru BRZ Premium (2014) its best car to pick if you want sell it after prelude finish.

you don't need to sell it if you want keep it. But if you min-max player like me, its better to sell starter cars after you finish the tutorial. since the game give you iconic NFSMW Car, BMW M3 GTR for FREE. by selling the starter cars you can use the money to upgrade that car instead since its more reliable than starter cars.
but remember, by selling starter cars, you will never get that unique car again (which have unique modification by Travis).