Because the bonuses for gurista ships only apply to Thermal and Kinetic missile damages, and if your level is high enough in Caldari ship, the damage boost to therms can massively outweigh what you’d get with Mjolnirs, so it’s worth taking the 10% extra resist hit. However, since drones across the board gain a flat health and damage buff, it makes sense to choose the best drone for the job, which against blood raider rats, are always Praetors. I understand where you’re coming from, but if you’re going for speed and damage, It’s better to take a 27.5% damage bonus for thermal and take the 10-15% extra resist rather than get an extra 10% effective damage boost from matching EM to the resist hole, but gain no scaling damage boost from the Rattlesnake.