I think Infernus is the better choice regardless, unless you are really into long, boring stretches of soul farming. Infernus has good raw power and great versatility, can be used in multiple farming setups (including delves). Pharos offers some raw power and control, but is primarily just used for soul farming, and while soul farming can offer progress, I’ve never actually needed to do it on any of my alts and even my main “coasted” past the necessity to do so with three star (what is now considered power four) kingdom tribute and into dawnbringer. You can be a lot more conservative with souls to get stars now than with the old power system, since leveling troops all the way that you don’t use is essentially pointless and the level 10 or 15 thresholds you need for early kingdom power stars take a fraction of the souls of leveling things to 20.
If you are after Pharos as just a stepping stone for Dawnbringer, remember that 20k souls an hour is still 64 more hours of hardcore farming, and even 30k souls per hour is still about 42 hours. Do you really want to put your nose to the grindstone that long for one weapon? You’ll probably want to spread your farming over many, many weeks, and not prioritize it to not burn yourself out unless you are really in tune with doing this kind of thing. Dawnbringer itself doesn’t really open up a lot of huge doors for you - speeds up arena farming to be sure and is a good weapon overall, but certain event and class weapons are often your anchor or win condition for tougher fights. The longer you put off farming for Dawnbringer, the more souls you’ll just gain passively that you can’t do anything with at all and the less of a grind it will be. And long enough, you basically get it for free (though it could be a long wait).