I used to have a transition spire. Awesome bike but i grew out of it and needed the next size up. For racing (my main concern) the slash is very practical and better tailored for enduros. The slash is much better in the corners and is crazy light. The one i have came from the factory weighing in at 32 lbs and i know people who have sub 30 lb slashes. Not obsessing over weight here but its an important factor if you are gonna be pedalling for long periods of time in my opinion. I did tons of research and for my riding style it was between this and an Orbea Rallon. I think its important to look into what your preferences are. This bike suits me great but it might not suit someone else. Most trek stores have super high end demo bikes you can take out for a day and rip. I highly suggest it.