Here are the specs of each.
This is a MC800C Electronic Speed Control for 5+ Turn Motors.
FEATURES: Operates motors that are 5 turns up.
SMD Mosfets with smallest internal resistance for minimal losses
and maximum power.
Digital variable modes "Power Control", "Hyper Brake", and
Optimum 3140 Hz digital High Frequency
Start Acceleration Function
4-Cell Operation possible without receiver battery.
External solder points for the motor and battery leads.
One Year Warranty
INCLUDES: One MC800C Electronic Speed Control w/ Reverse and Brake/ Futaba J
receiver connector, and On-Off Switch.
One Plastic Adjustment Screwdriver
Three Motor Capacitors
One Schottky Diode
Four Black zip straps
Double Sided Tape
REQUIRES: Futaba J compatible receiver.
Female bullet motor connectors for motor, use TRIC5500.
SPECS: Capacity: 4 to 7 cell batteries
Motor Limit: 5+ turns
High Frequency: Yes, 3.1kHz
Connectors: Futaba J
Bullet Motor Wire: 12 gauge
Weight: .62 oz
This is the MC600C Forward/Brake Sport Speed Control by Futaba.
This will handle 10 Turns and above.
++ Additional Technical Information Will Be Added As It Becomes Available. ++
FEATURES: All connectors and heatsink are pre-installed.
Has Software Protection against: Heat, Current Overload, Short
Circuits, (It is NOT protected against reverse Polarity).
Easy Push Button Set-up.
Forward and Brake only.
Can handle 4 to 8 cells.
Will handle motors of 10 Turns and above.
INCLUDES: One MC600C Sport Speed control,
Double sided tap
REQUIRES: Receiver that accepts Futaba J connectors.
SPECS: Dimensions: 1.0"x.91"x.63" (25.4mmx23.1mmx16mm)
Weight: .53oz (15g)
Freq: 2.5kHz (2500Hz)
BEC Voltage: 5.0
Wire: 14 Gauge
The 800C has alot more setup features, cand handle fewer turns and has a lower internal resistance. Both are good esc's so if your not a serious racer and your not going to use the features then there's no reason to spend more for the features. By the way, why not just send the esc you have in to be repaired?