Most of the time when I'm using a phone I'm doing something intensive (rendering a web page) followed by long periods of light use (reading the web page). So I

Most of the time when I'm using a phone I'm doing something intensive (rendering a web page) followed by long periods of light use (reading the web page). So I think that running fast for a short period is a good thing for phones to be doing. And making a phone faster will almost neccesarily drain the battery faster. The important metric is task energy where you multiply the time it takes a phone to do some task by the power it consumes while doing it to figure out how much energy was needed overall to do it. By that metric adding more cores usually has less of a negative effect than speeding up a phone by upping the clock speed or the size of the OoO structures.