Gouie

Hey guys, I'm looking for some honest advice here. I'm ready to purchase my first and most likely last bike for a very long time. 100% of my riding will be trail. I'm 6ft, 170lbs. So far I have narrowed the search down to the WR and XCF. As mentioned, I'm looking for some honest advice. I'd prefer not to hear go blue or go home. Not only am I torn between the yami and ktm, I'm also wondering if the 250 is enough or should I go to the 450. I have ridden in the past but that was 15 years ago. For all intense and purposes you can call me a newbie. The problem I have is I don't want so much bike that I'll be afraid to hop on the thing but I also don't want to "out grow" the bike the first year. HELP!