Modern Vespa

Is one preferable to the other?

Function is so basic I guess they are pretty much the same. But with SIP you have the option to buy the version with reserve alert, if desired. My 2 cents

Functionally, they seem to be identical.

I just throw one in with an order of other parts from whichever site I happen to be on and couldn't tell you which is which after the fact.

I've had issues with the BGM tap not flowing well on reserve on my GS. I'm switching to the second version of the SIP tap but can't report on results.

Scooter speed had both. Went with the sip. The angle of the barb maybe matches the stock one I have. Also had problems with the BGM 1st gen on a large frame in regards to getting airlocked when running onto reserve.

It's a thing. At least it was with the earlier version:

I've installed both, SIP 2.0 is a better design. Larger holes and better angle for the hose… you can install a 8mm hose on the SIP, the 6mm will be very tight.

The BGM is a boxed version of a tap made by OMG… it works, but definitely slower flow than the SIP

I have a recollection that someone on here documented a case where one of them (don't recall which, too lazy to search) had a tap which had the holes almost completely blocked with flashing when it was DOA and they tore it down.

If folks say go with the SIP, I'm not going to argue--like I said, I've used both successfully in the past and have no complaints about either one, but it sounds like the SIP has a better spec.

Black seal= SIP (holes are around 4.8mm)
Red seal = BGM (holes are 3.9mm)

The tank tap nut is the same size, so the SIP is much bigger

The sip one arrived from Scooterspeed today! Only ordered it Sunday night! Great service! Looks like the "reserve" has been corrected to be at a useful level. Come with a nice looking lever with 2 different holes for small frame and large frame I assume. Happy with my choice.

I have a sip 2 fast flow, it certainly improved fuel starvation issues i had on my px when my tank got very low on fuel. For a cheap part certainly worth it and ironed out my issues.