Can i ask why? This is my first rack. Just trying to look through my options. Lol
For one the ARS 70 series tubs can be purchased with a built in water dish molded into the tub. This means they can't slide around and spill water everywhere. They also have a completely flat bottom and floor, which makes heating and cleaning much easier (The V70 is flat on the inside as well) The ARS tubs come in grey or semi-clear. You can get the integrated water dishes in either color. Overall I think the ARS tub are a higher quality tub, (design and materials)
The IRIS CB-70 tub was designed for household storage, the V70 and ARS 70 series tubs were deigned for reptiles (based on the CB-70). Either will be great, but I like the extra options/quality you can get with the ARS 70 series