I'm no expert on this topic, but I'll throw in a little of what I know. In short, yes, they are similar, at least, I believe they're both similar to Shotokan, so they must be similar to each other. I can't really comment on their effectiveness in self defense, but Kubota Sensei has been involved in instructing many law enforcement groups.
Gosoku-Ryu is the style created by Takayuki Kubota.
You can find detailed info at their website.
http://www.ikakarate.com/
He was a Shotokan instructor before founding Gosoku-Ryu. The Kubotan is named after him. He's done many movies. I believe he introduced the tonfa-like baton the U.S. police departments. I have one that i think he gave to my mother when she worked for Black Belt Magazine back in the 70s. His hombu dojo is in the Glendale, CA, area.
I know that Shindo Jinen Ryu is also similar to Shotokan, but I'm not familiar enough to say how. We sell two videos made by Yamazaki Sensei of the Japan Karate-do Ryobu-kai titled
Japanese Karate: Shindo Jinen Ryu and
Japanese Karate: Shotokan and Ryobu-kai, but I haven't watched them.
Here's the Japan Karate-do site.
http://www.jkr.com/
I don't know what part of the country you're in, or even what country, but I know several instructors in both styles, and I can't think of one that I wouldn't recommend if you're looking for traditional Japanese karate.
