Systemwide upgrades

I'm a Diamond Member and fly almost exclusively long haul international flights. I typically use all of my systemwide upgrades. However, I've noticed lately that "M" class tickets are extremely expensive (>$4,000!). My company is trying to reduce its business travel expenses and is forcing me to buy lower class tickets.

Delta's systemwide upgrade limitations are making me consider transferring my business to AA because their systemwide upgrades are available for ANY economy fare.

Am I wrong to consider leaving Delta because of this?

Thanks!

JW