Historically, the "Normal" level for coils (this is an 'average' coil, so some are different than others) on a 3.7 volt battery setup like yours is 2.3ish - 2.5 ish ohms. That's a fairly cool vape that has a long battery life.
Also, historically, the eGo units are/were 3.4 volts (regulated).
Now the 1.5 ohm stuff was mostly used by people for the 3.4 volts e-cigs. That's not to say that people didn't use 1.5 on higher voltages, but again I'm talking averages here.
So, the 2.0 ohm stuff is what I generally use and recommend on 3.7 volt stuff. The 1.8's are OK too. The 2.3/2.5's were too cool for me.
I found that the 1.5 ohm stuff would burn certain juices at 3.7 even when dripping (like fruit flavors). This was after the initial drop in voltage from the fresh charge.
But coils vary. I find the top coil cartos to be the hottest, so would suggest above 1.5 on those even with using a drip tip when needed/possible. YMMV.
