HOW MANY BIKES ARE YOU PLANNING TO CARRY?
Roof racks generally are great for two bikes, three is pushing it and it might not fit depending on the width of your car. If you plan to transport more than 3 bikes your best bet is a hitch rack,which can usually allow you to carry between 4 to 5 bikes.
WHATS YOUR BUDGET?
Though roof racks look much cooler you have to buy the rack aka crossbars and then the individual trays and locks which could mean some serious coin to hold two bikes, however if you go with a hitch rack they tend to be cheaper and more efficient and can transport more bikes.
WHAT ELSE ARE YOU PLANNING TO CARRY
The hitch racks are cool when you just transport bikes however if you kayak or snow board then you might want to go with the roof rack and buy the attachments for each sport.
In addition if you go camping a lot and need the extra trunk space you can always purchase a roof bag or a sky box in various sizes for your camping needs.
