The decision of which end of the bike you should start with (front or rear) when upgrading suspension (if you don't plan to do both front and rear at the same time), is based on what suspension aspect you are trying to improve first. The question you must ask yourself is "Do I want to improve my suspension more in terms of handling and control, or comfort/ride quality?"
We design our suspension products with the framework that about 80% of the handling and control of the motorcycle comes from the front suspension, and about 80% of the ride quality, or (how comfortable the ride feels), comes from the rear suspension. Keeping this idea in mind, we designed our AXEO Front Fork Cartridges with a focus on improving the handling capabilities of the motorcycle, and rear suspension products, whether it be air ride or coil shocks, are designed with a focus on improving how the ride "feels" or (how comfortable the ride is). When used together, our products are designed to work in unison and complement one another for an overall improvement in ride quality and handling to achieve a balanced chassis.
Keep in mind, that both our front and rear suspension products if used individually will improve "handling/control" AND "ride quality" immensely over the stock suspension. Depending on which end of the bike you choose to upgrade first, will determine which suspension aspect you want to focus on improving the most.
Please keep in mind there is nothing wrong with using only our rear coil or air shocks with a stock front suspension, or our AXEO Front Fork Cartridges with stock rear suspension. Generally, the feedback we receive from customers that only upgrade the suspension on the front or rear of the bike, is how much more they notice the stock suspension on the other end is lacking.