My experience: 2006 (heavy snow year), KM date of June 14 (June 18 up Whitney, June 19 on Forrester, June 20 on Glen…see the TJ for the rest…)
Axe: Camp XLA210 - it’s fully rated and light. Saved my butt on Glen, where I fell heading up. Saved me from turning around when I got to the top of Glen and looked at the north side (VERY steep and very scary). On my way up Glen, I met a couple heading back south after seeing the north side - too high a pucker factor for them without axes. The pucker factor on Mather was also very high - I’m glad I had the axe for the scary as heck traverse on the steep terrain above jagged rocks just before the pass. The axe was worth every ounce and dollar. I bought it just for the PCT and haven’t used it since. Carried it from KM to Tahoe, although I could have sent it out at Bridgeport (the Elephant Back isn’t bad).
Crampons: Carried and seldom used 6 point insteps. I wouldn’t carry them again. The fall on Glen was with them on. If you wait just a little bit in the morning for the snow to soften and are appropriately careful and deliberate with your footwork you’ll be fine without them. You can also chop steps where you need to with the axe.
If you’re unsure of getting a lighter axe, wait until Agua Dulce to make your decision. At that point, you’ll have a good idea of the spring storm / snow melt situation (recall that LOTS of the 06 snow pack happened in mid April, delaying the melt off).
If at Agua Dulce you feel the need for a lighter axe, take a ride into LA to the REI or other out door store and get a light axe. Mail it to KM from AD. Otherwise, have your heavy axe sent to KM for you (or send it to AD now, then forward to yourself at KM from AD, or send home, as the situation dictates).
Getting a lighter axe also depends on your Sierra resupply stragegy. I went straight through to VVR, so I was very pack weight critical (~45 pounds total leaving KM - bear can, axe, crampons, 11 days of food and a full liter of fuel were what caused the killer load). If you’re cutting out for resupply post Forrester the extra pound or two of your existing axe vs. a XLA 210 or similar light axe won’t be so bad.
Markv - I will suggest that in the end it’s not about guessing, it’s about finding the right combination of skills and equipment for the terrain and (estimated) conditions you’ll encounter given your level of risk tolerance.
Token Civilian