Some difference between Cuisinart ice-21 and ice-30BC:
The ice-30BC is larger, holds up to 2 quarts that is 0.5 quarts more than ice-21.
The ice-21 is sold for $30 cheaper than the ice-30BC on cuisinart.com
Design of the On/Off control is different.
Freezing Time on Cuisinart ICE-30BC is shorter.
The Mixing Arm is redesigned on ice-30BC, but it is small, only scrapes one side while instead of scraping both sides like the ICE-21, thus leaves more buildup on the sides.
The ice-21 produces less ice crystals.
ICE-30BC is noisier.
Compare Cuisinart ICE-30BC and Cuisinart ICE-21
| Cuisinart ICE-21 | Cuisinart ICE-30BC | |
|---|---|---|
 |  |
|
| Price | $59.95 at cuisinart.com on 2014-07-16 | $89.95 at cuisinart.com on 2014-07-16 |
| Capacity | up to 1.5 quarts | up to 2 quarts |
| On/Off Control | Switch | Dial |
| Freezing Time | between 16 hours and 24 hours | between 6 hours and 22 hours |
| Weight | not specified | 13.5 pounds |
| Dimensions | not specified | 8.25" x 8.00" x 11.25" |
| Freezer Bowl | Double Insulated Freezer Bowl | Double Insulated Freezer Bowl |
| Feet | Nonslip Rubber Feet | Nonslip Rubber Feet |
| Cord Storage | Unused cord can be stored into the base. | Unused cord can be stored into the base. |
| Warranty | Limited 3-year warranty | Limited 3-year warranty |
| User Manual | User Manual | User Manual |
Overall, according to users’ experience and reviews, the ICE-30BC is easier to use, but the ICE-21 makes better ice cream.