I understand how people are up and down about the factory tour. It's 40+ minutes on the train from Sendai and then if you're not there during the weekend you have another 30-40 minutes walking to get into the hall. I did it on a day where it was probably 33°C and I'd already gone to see Yamadera. The humidity in the area is oppressive, and one of the Japanese tourists told me the area was picked in part for the humidity and how it would help create a great whiskey.
Japanese tours can be a little cold. You have to look at things through windows and a lot of what goes on in a distillery is just looking at pipes and tanks. You don't even get to see the Coffey still, though they will point out the building. I've heard that the VIP tour gets to see a barrel being charred, but you have to be a VIP in the minds of Nikka Whiskey, not in your own mind.
The best part is after the tour. There's a small bar where you can get short pours of Nikka for very little money. Where else can you even find Taketsuru 12, 17, and 21 and when I went the short pour of 21 was only ¥500! There was even a special edition Taketsuru that was ¥7,000 for a very short pour and I was glad I tried it.
I'd recommend finding a non-driving way to get there so you can taste a little of everything. During the tour they tell you there's three types of Yoichi that they blend to make the single malt (it's my understanding that they sort the barrels into different flavor categories) and I had a taste of the Peaty and Salty was worth tasting on its own.
Just remember, it might seem long way to go but just going from Osaka to Kyoto is going to take you longer and to me those cities are right next to each other.