To each their own, I'd take the train any time, as long as my case had wheels! From the south entrance to Shinjuku, turn right after you pass the ticket turnstiles. Narita express leaves from one platform, depending on which side, it's either track 3 or 4. There are electronic signs that tell you where to stand for your particular car number, which is on the ticket. The "schlepp" from the south entrance is about 150 yards.