I was surprised by your answer to a previous question, that Harrenhall would’ve made a good capital location for a Targaryen dynasty (sans curses) Can you elaborate on why? Were you suggesting it’s better spot than Kings Landing? Or just a good alternative? The only negative that came to me comparing the two is lack of ocean trade at Harrenhall.

My main issue with King’s Landing has to do more with Aegon’s decision to keep the Crownlands small, only absorbing a small part of the Riverlands and Stormlands, which had massive ramifications for the strength of the monarchy once the dragons died. To be fair, this involves a heavy dose of presentism, as Aegon had no idea that the dragons would die out.

However, Harrenhal does have some benefits: 

1. It’s an already extant castle that’s big enough to hold the entire political class of the nation, and we know that there’s enough space there to hold “the fourth largest city of the kingdom.”
2. It still has ocean trade via the Blackwater Rush, and if you built a relatively short canal, you could have access via the Trident as well. 
3. It’s more centrally located, which means travel and communication between the capital city and major centers of power out in the provinces would be faster for the more northwestern half of the kingdom. That should also cut down on inter-kingdom conflict more, because it would be impossible to attack another Great House without going through them first.
4. If the Riverlands plus Crownlands was the personal fiefdom of the monarchy, you’d deal with the weak monarchy and weak Riverlands problem, since royal government could ensure that the abundant natural resources of the region were fully utilized.