Though the model numbers are similar, there are some big and slight difference between Shark MV3010 and MV2010.

Shark MV3010 vs MV2010
images from manufacturer

Cleaning Modes
Both of the Shark Vac-Then-Steam MV2010 and Shark Rotator Vac or Steam MV3010 have 2 operating modes: vacuum mode and steam mode.
But the key difference is that the MV2010 comes with only one nozzle, when operating in steam mode, you attach a steam frame to the nozzle.
Whereas the MV3010 has no steam frame, but includes 2 interchangeable nozzles: 1 vacuum nozzle for vacuuming and 1 steam nozzle for steaming.

Vacuum Nozzle:
Another big difference is that the MV3010 vacuum nozzle has brushroll that can be turned on or off for cleaning carpet and bare floors, while the MV2010 vacuum nozzle has no roller but just suction only mode.

Steam Mode:
While using the MV2010 steam mode, there is no options to select, just on or off.
Whereas the MV3010 steam mode has 3 options: Dust mode, Steam mode, and Scrub mode.

Water Tank Location:
The water tank on the MV2010 is located in the middle part of the unit, while the one on the MV3010 is in the steam nozzle.

Warranty:
The MV2010 carries a 1-year limited warranty whereas the MV3010 is backed by 3 year limited warranty.

Cord Length:
The MV2010 has a 30′ cord whereas the MV3010 has a 25′ cable.

Weight:
The MV2010 weighs 8 lbs whereas the MV3010 weighs 10.9 lbs in steam mode and 11.4 lbs in vacuum mode.

Dust Cup Capacity:
MV2010: About 0.8 dry liters max.
MV3010: 0.5 dry quarts to the fill line and 1.2 dry quarts real usable capacity.

Technical Specs:
MV2010:
Voltage:120 volts, 60hz
Power: 1550 watts
Water Capacity: 300 ml (10 oz.)

MV3010:
Voltage: 120 volts, 60hz
Power: 1200 watts
Water Capacity: 500 ml (16.9 oz.)

Accessories:
The MV3010 includes a Crevice/Brush Combo Tool that the MV2010 does not have, and 2 Multi Purpose Steam Pads.
The MV2010 comes with 1 All Purpose Cleaning Pad, 1 Heavy Duty Cleaning Pad, Steam Frame, 1 Replacement Post-Motor Filter and 1 Replacement Dust Cup Filters Set.

Color:
The MV2010 is in lavender whereas the MV3010 comes in white with red.

Some other difference:
The MV3010 has a carry handle whereas the MV2010 uses a carry grip but no carry handle.
The dust cup on the MV3010 is easier to empty, you just press 2 buttons to get the job done, but the MV2010 requires you to twist the dust cup cover to dump the trash.