Better to go up or down in board size?

Hi guys just wanting to get your opinions on whether it is safer to go above or below your estimated board size.

I weigh 190lbs but am just about to start training to hopefully cut down to around 180 and I am about 5 foot 10 with a size 12 boot. I have no park experience but am looking to change that this season (I live in AUS).

I am currently in the middle of selling my burton bullet. I am planning on buying a rome tour because I think it will be a decent upgrade without me having to spend too much money and I like the look of them. My Bullet is 157cm and I'm pretty comfortable riding it. I was just wandering if anyone would think I'd be right to go for a 155cm tour or just play it safe and go for the 158cm? The waist width of both of them are larger than my bullet so I'm not worried about them being too narrow or anything.

I'm really only torn between the two because I prefer the colour of the 155 over the 158.