Mini-Z is a lot cheaper than 1:10 since the requirement of equipment and the parts itself are both cheaper than larger size RC.
You can run Overland and Monster outdoor but not the Racer because of ground clearance.
Overland & Monster are 2WD only and very few people play them now.
IMHO, the first upgrade should be stacking FET which costs about $2XX at the track. Replacing the original FET allows you the flexibility of running other modified(faster) motors WITHOUT burning up the FET.
As the name implies, "Mini" means it takes up alot less room than a 1:10 in your house.