you have to take powerdistributor size of the attacker into account, too. e.g. a cutters or pythons PD is large enough to fire pulses 20 sec+ with zero pips to WEP ;-)
obviously, more speed=better, more shields=better.. but when we are talking about "exploration builds", we are talking about compromising defense with power requirements (powerplant size),weight (jumprange) and heat. e.g. - obviously a cobra mkIV will be "more safe" with A-class thrusters, A class PD, a L5 dirty drive tuning, A4 shields reinforced or thermal resistant, 3 or 4 a-classs boosters, a class 4A scb - and some additional HRP ... but this build will hardly be called an explorer build ;-)
so, the question stands - what gives you more safety for the same weight, heat and power-requirements?
and this can only be answered depending ship-types. a ship(build) above a critical speed, will win more safety from thruster upgrades (which add to powerrequirements and heat) and powerdistributor modding (for constant boost), while a ship below that critical speed will only gain very small to none advantages from thruster and powerdistributor upgrades. the anaconda is for sure one of the ships missing critical speed, the DBE is exactly at the turning point (e.g. it can get fast enough to outrun NPC in a short time, if you take hits on weight and heat for A-class thrusters and modify thrusters to the max.), and the AspE depends very much on thruster class and quality.
also, there is a diminuishing return - the difference, if my cobra mkIII boosts to 520 m/s (which it does) to it boosting to 480 m/s is close to zero pve.
tl,dr: if you rely on shields to survive, focus your power, weight and heat management there - if you rely on speed, put your focus on thrusters and PD. have in mind, that if your only target is to survive and encounter, there is no need to waste power, weight and heat above a certain critical value.
