I have both. Didn't think I would like the V3 as it looked a little funny in the pictures. There are several differences between the two, most of which have already been mentioned. The V3 has a better OLED screen. The engraving allows the device to be gripped much easier, I.e, it doesn't try to slide out of your grip as easy. It's not such a fingerprint magnet either. The top drip well cap is removable and larger allowing easier cleaning and better air flow.
The V3 can be ordered with or without the rhinestones. Don't laugh, the wife loves her "bejeweled" device. The RMS setting on the V3 is not changeable but would be highly recommended and generally considered preferable over an average mean setting. Vapers petitioned the manufacturers several years ago to add RMS because it is a more consistent setting and one desired by most vapers. The only negative is that the V3 does not come in stainless steel, which is a more expensive and higher quality build imho. Also, the V3 looks much better in person than it does in the photographs. Surprisingly, I now prefer it to the V2, it just looks cooler and better executed. I find the V3 slightly better for all the reasons stated. In reality they are very close. If you see them up close, it will make the buying decision easier. You simply cannot tell from pictures alone, you really do need the touch, the feel, the heft, etc. For example, I thought I wanted a Tesla because it looks cool in the pictures. Picked up one yesterday to check it out and it's made of light aircraft aluminum. I thought it would feel more substantial, like a stainless steel mod. I didn't like it and took it off my wish list. A picture may be worth a thousand words, but it's a lousy way to buy a mod, and looks is not the only reason to consider one over the other. Check it out, you'll see., Welcome aboard, good luck, congrats on getting here and Vape On!