specs for x-4:

Stm 80
Exp 360
Stm/Exp 0,2222
Dumplings 48
Stm/Dpl 1,6667
Coins ~10,000
Life Crystals: 6 (Chance of 2 more)


Bonus Stage:

Stm 80
Exp 160
Stm/Exp 0,5000
Dumplings 90
Stm/Dpl 0,8889


x-4 + BS
Stm/Dpl 1,159420


as expected, phase 2 is more lucrative than phase 1.
i recommend you to do the BS if it spawns.