These are all variations of the same antenna.  The differences are with the range, coaxial cable lengths, coaxial cable colors and if the coaxial cable can be removed or not.   In essence these are all the same antenna with a little variety in the accessory options.


Here is a list that will hopefully help you determine which antenna best fits your needs.


Antenna Model
Curve 30
Curve 50
Arc 40* 
Originally offered as 
a Best Buy Exclusive.
Flow*

*Same antenna as the Arc 

but was originally a  

Mohu offered exclusive.

Flow Plus



Range
30 miles
50 miles
40 miles
40 miles
60 miles
Is it Amplified?
No
Yes
No
No
Yes
Amplifier Color
N/A
White
N/A
N/A
Black
Coax Length
10 foot
16 foot
10 foot
10 foot
10 foot
Coax Info.
Detachable 
Detachable 
Affixed
Affixed
Affixed
Coax Color
White
White
Black
Black
Black
Size
12 X 8 X 2.5
12 X 8 X 2.5
12 X 8 X 2.5
12 X 8 X 2.5
12 X 8 X 2.5
Image
Link