With the release of hard tower levels 51 to 70 and its accompanying eternal equipment, the base damage divide between legendary/mythic and tower gear is finally closed. This video will show you how to reinforce with gold and catalysts (obtained from the frenzy chests that GM mails out daily) and my written commentary at https://clad.life/ also suggests some utility options.
Tower equipment is arguably cheaper in the short term for +150% damage weapons, as enchants go up to level 20 instead of 30 and require runestones and gold, instead of runestones, rune powder and gold. In the long term though, once you've maxed out the 30 levels of legendary and mythic equipment, you can use orichalcom, elemental stones and gold upgrade them, so you can save on runestones, rune powder and some gold as opposed to farming and levelling tower equipment every time a higher tier lands.
Also, since the damage gap has been closed, you can also find more utility in the equipping a fury steal or cleanse weapon without losing too much damage. As these weapon effects only occur on a non-skill hit, it's recommended that you only equip them on heroes that attack without skills, eg Zhao Yun, Michael and Prince Arthur just to name a few.
If you're into immediate gratification then focusing on tower equipment is the way to go; if you're into saving resources over the long term, then we are one and the same (I do use some of the tower weapons for Mythic Raid and Ruins Explore), and I suggest focusing on maxing out as many sets of mythic or legendary equipment as possible now, and making use of orichalcom to upgrade them as and when new tiers of equipment land.