70s Lava Lamp question

Hi, just joined last night so I could ask about this, so I'm sorry if I don't contribute much! Hopefully someone on here knows about this. It's not super important or a huge deal, just curious.
Been shopping for a "coach" model of 70s lava lamp and noticed that despite being almost entirely the same, some have a knob on the base, and moldings around the handle prongs, whereas others have just empty holes that the prongs go in to and no knob. Also the prongs/handle on the knob one are two separate pieces instead of one. I had a model with the knob, and as far as I could tell it didn't actually do anything? So I was wondering if there are any significant differences in these that I couldn't tell from a photo, or if they are just different production runs and they went cheaper on materials the 2nd time around or something? The knob variant seems to be more rare, as I've found a bunch of the ones without it and only two with it.
Here are some pictures of what I'm talking about:
vs

Thanks!

 

These are later knock-offs and not true original Lava Lamps. As such, can't tell you anything definitive about these. The knob is a facsimile of the fill spout on an oil lamp. Agree that the second version would be cheaper to make but have no idea if made by the same company at different times or just different knock-offs from different companies.

 

Thanks! The first one would be about $60 more than the second one, so I'm trying to decide if it's worth it. I imagine true original ones would be much more expensive.