Well I don't have any input on the 6 inch..... but my 9 inch is good! I bought a used Nook online for $75 years ago and I'm loving it! I like to watch YouTube videos on it, read OGR, and other activities. I didn't think I'd use it over my phone or laptop but it truly has found a niche that it's very useful in! Plus, if you use it to control the WiFi module on your MTH trains its just perfect!
I guess my suggestion is, try to find a 9 inch tablet. Three inches doesn't sound like much but when looking at a video or OGR online it makes a difference!