Okuhida or Gero Onsen for a night

Hi
Would need some advice in choosing the better Onsen town between Gero and Okuhida. Will be travelling from Matsumoto after exploring the castle so around mid day. Both places looks amazing. Which one is more authentic and is better in terms of experience? Can we travel to Gero straight from Matsumoto or have to go via Takayama?
Thank you

I am not sure what you mean with "authentic". What expectations do you have from a hot spring town?

The towns could not be more different:

Gero is a built-up town with lots of concrete and lots of lodgings of all quality levels. Some of them offer wonderful overnight experiences.

Okuhida is high in the mountains. Very rural. It consists of several small villages. Some are a little larger, others smaller. They tend to be smaller, rustic, traditional ryokan, although there are some large complexes, as well. I consider Okuhida to be among the best places in Japan to experience a traditional, rustic onsen experience.

So, if you are after a rustic experience, make sure to select Okuhida.

Can we travel to Gero straight from Matsumoto or have to go via Takayama?

By bus via Takayama or by train via Tajimi and Minoota (or Nagoya).