GX cs4i

Great deal. Mine was over $100 more.

If I were making the choice it would be for a GX CS-4 (with external power supply)
The internal supply is just not worth another $66 for me

The CS4-I wasn't on market when I purchased my CS4. I think the internal or external power supply decision should really be one of intended use. I use mine more in the field so lugging the extra size and weight wouldn't be practical in my small pickup. If it never left the house, maybe internal would be okay. However an external power supply is much easier to replace if/when one goes kaput. Decisions, decisions, decisions. Once you make them got to live with them.
Got mine direct from GX because of a previous drawn out hassle over a refund with Amazon, actually cancelled my Prime account and do my best to purchase elsewhere now even if it cost me more.

I made the decision to purchase the external PS version and sink the savings into 3 yr protection for less than CS4-I and 1 yr coverage

The price difference was irrelevant to me. I purchased the model with outboard 12v supply because I wanted the waste heat dumped outside the compressor case and because I have several alternative12v sources for my short-wave radios.

I needed a compressor so I got one on the way. Will be here Friday.