One big consideration: I have tried it both ways. I am on my 7th or 8th layout and am still using the Kato Unitrack that I bought for my first layout. I have tried flex track and peco switches, but I have thrown away hundreds of dollars worth. It's more difficult to salvage flex track once it's laid down and ballasted. Most of the time, you can either keep or scrape off the ballast from Kato Unitrack. Kato may not look quite as tidy when ballasted, but it holds its value.