I saw you on Feffox and Evis last days so here is my experience on them with adj chip compared to mod2600.
But first the most important point: I love my Mod2600 and you definetly feel more badass with 54instant heal + 54 over time then with chip. 
172Hp, 32 Evader, Weapon mostly Shagadi + VI so smth like 56dps.
Feffox: On youngs those are very nice to hunt with adj chip. But on Mature and bigger I needed some extra heals from fap after big hits. This might get better with more HP. So i used a small armor there.
With Mod2600 its like on every other mob that doesnt hit often but big. Very nice. Young and mature easy to do naked, but due to the fact there are also alot olds I used small armor (Canis + 2A plates here compared to Imp B.E. 5b with the chip). But with both Setups they were doable and both very eco.
Eviscerator: Hunting them alot naked with Mod2600 atm. And its very easy. Have to heal very rarely during mob, at least on Gen01/02. Most of the time its 1 heal after a few mobs. So I thought, chip might be enough here.
And yes, tried with chip and had to heal only once with fap on 1k cycled (ninjas :P). I had 1,64 decay with chip on that 1k cycled so total defense cost at 0,16%. With Fap I have like 7-8Ped decay after 1k cycled. Dont know exactly, neeed to test it. So like 0,75% defensive cost.
Now mobs like bigger Feffox, SEGs, Prots, big Shubs, big Ambus, big Atrox. So big hits but not very often: No chance with Chip, awesome with fap! 
(or better: you need (bigger) armor with chip)
So its a bit about your playstyle: With Fap you will need less armor on a few mobs. With Chip you can save more PEDs on lower mobs. With fap big mobs suddenly become doable.
Fap will get even more awesome if you have a friend healing you with it. 
And it will get better, the more HP you have.
But looking at price: you safe way more money with chip compared to fap if you count the price to buy them in. But with fap you get (imo) the more awesome tool.
S1 wrote about adj chip + mod2350. Thats probably a pretty awesome combo as well. But never tried it. I prefer the huge heal/click of mod2600. 
edit: btw.: you can even improve Eco on Mod2600 with eco enhancers. Average break-rate is 850 klicks. So it will save you 2,5% decay/enhancer, more if you can get them cheap.
But it will need like 16k+ TT cycled on Fap to cover Tier cost with it

So better only tier it if you want it for the heal enhancers and see eco enhancers as bonus.
edit2: 20k for fap? Mod2600 + adj chip
Even if its a bit “overkill”.
edit3: best would be just try both to see what fits your playstyle better 