My foundation was mainly built using H3/H3Neo.
Here is a short summary from my experience on a Walnut/Spruce blade:
MXP is faster than G1, non linear, mid-throw, a bit more spin. Feels crisp on contact. Hardness feels similar to G1.
Fastarc G1 is faster than H3 but slower than MXP. It is linear in response like H3. Higher throw than MXP, but a bit
less than H3. Spin is very good, maybe a bit less than MXP on more powerful shots. Hardness is similar to MXP, and
both are softer than 40degree H3.
Fastarc G1 conveys better blade feel than MXP. If you use a carbon blade, it doesn't make much difference though. Although MXP is faster and has a lower arc, my skill level worked better with G1 (i.e. I won more games with a more
consistent loop due to the better linear response and blade feel and overall better control).