It depends on YOUR personal/judgment of value - as they are very similar. In my experience EITHER is good for the application and does the job. Is the Lastolite vs Interfit “worth the difference?” If value is the criteria then NO.
[just like reflectors/softboxes etc. by Lastolite vs Interfit may not be considered “worth the difference”; I own both, however prefer Lastolite quality].
Re: Reflector Brackets - having said the above, for endurance and transport I prefer the WESTCOTT, or LASTOLITE as the main position/adjustment handle & perimeter bracket casing which takes any cantilever effect appears to be made of stronger plastic [WESTCOTT - nylon & has two extra ribs in its design, which would assume are for more strength; LASTOLITE – nylon], rather than the INTERFIT’S lighter material [appears to be a polystyrene, possibly subject to more stress fracture over time]. Also, Interfit’s plastic main position/adjustment handle (not bracket) is a bit bigger (approx 25% bulkier) and Interfit’s total reflector bracket folded LOA is 2” longer, which is inconvenient for me, for transport or travel & occasional fly location photography application, in a 26”(66cm) checked luggage/suitcase which accommodates things up to 29”(74cm) diagonally. [Westcott & Lastolite just fit in the suitcase when rotate bracket under at the pivot].
I prefer (based on a criteria of compactness/sturdiness):
1st - WESTCOTT (I have two of them) [Mfr # 1100]: http://www.bhphotovideo.com …1100_Illuminator_Arm.html
or LASTOLITE (I have one of them) http://www.lastolite.com/reflector-accessories.php
2nd - INTERFIT ( I have one of them)
Others will have different opinions.
Good luck on your selection…