Recomendations Hogwarts express vs Polar Express O scale

I've got both of them.  The Polar Express gets more track time.  We also use it for a kid's Polar Express themed program at our local MKT Depot museum.

They both have been trouble free so far.  I've gotten the expansion pieces for both of them.  The Trainsounds tender for the Polar Express has a reasonable sound package - steam chuffing, bell, great whistle.

On level track the Harry Potter does out smoke the Polar Express.  But introduce a grade on the layout and the added current draw going up hill increases the smoke output on the Polar Express. 

There have been articles about replacing the stock smoke unit on the Polar Express with a fan driven unit that will smoke better - this replacement is rather involved, so you need to be handy with tools and willing to hackey-chop your locomotive.

If kids are involved, freighttrains do offer more 'play value' than passenger trains.  I did not get any passenger equipment until I got back into trains as an adult.

All in all, it comes down to what you reall prefer. 

I've got a bit of a personal connection with the Polar Express. The Berkshire in the Polar Express movie was inspired by the Piere Marquette Berkshire #1225 that was on display at Michigan State University for many, many years before being restored to operational status.  I remember climbing around on it as a kid several times.  Then, as an engineering student at MSU, I remember seeing pieces parts from it waiting restoration in the basement of the Engineering building.  Later still, while I was living in East Lansing, the boiler had gotten certified, so, for the homecoming game, they got a head of steam up and blew the whistle for every State touchdown.