Survivor suits occupy the ‘normal’ layer whilst ESAPI occupies the ‘outer’ layer.
Personally I like going for light survivor suit and then add an ESAPI on top of it as well as arm guards capable of blocking and some light-medium strap/outer leg guards.
Light survivor suit also has the most efficient encumbrance to protection ratio, with heavy coming out just behind and regular having only slightly better than half of light’s efficiency.
Even though heavy and light have comparable efficiency, there are other pieces (such as the simple ‘steel arm guards’) with greater efficiency than the both of them, that’s why I like using the light version as a foundation since the heavy already encumbers you so much.
TL;DR for below: How I do my dumb efficiency calculations:
(Add total protection values together then divide the result with encumbrance, higher value = more efficient. Coverage values are not as simple to put into a calculation as its impact is relative to other pieces protecting the same part, if you already have a decent amount of guaranteed DR from say a light survivor suit, it helps offset those 15% of hits an ESAPI will let through and in turn increases the value of your ESAPI.
For the sake of lazy calculations, you can multiple the protection value with the coverage %, 50 + 90 = 140 x 0.85 = 119 / 10 = 11.9. But again this does not really tell you everything, having 119 defense with 100% coverage is immensely more powerful than having 140 with 85%, therefore this is only usable if comparing gear which are both sub 100%.)
While I’m already ranting, who would seriously ever use the regular survivor suit? It needs a buff.
Light survivor + ESAPI = 6/8 100%, 50/90 85% = total 17 encumbrance
Regular survivor = 8/12 100% = total 15 encumbrance
Wait, that’s possible? Goddamn gonna have to get around to that.