With the other two new Perks, and with most of the other seven, you can clearly discern a better option between the two skills available at every five levels. But for a lot of this one, it depends on what Perk weapon you get. If you get a Commando, Gunslinger or Swat, go for Tactical Reload at level 5. Heavy Weapons training, on the other hand, will boost reload speed for Demolition, Sharpshooter and Support Perks.
Just when I was starting to think that the Survivalist Perk was a lazily designed throwaway, I came across the level 15 upgrade Weapon Harness, which should be your choice every time - never go for Ammo vest. Weapon Harness finally makes this Perk's ability to wield multiple different types of weapons worth it.
The thing is, sure you might be able to use different Perk weapons, but that doesn't mean you'll be able to carry them at the same time. Killing Floor 2 uses a weight system, that's capped at 15. So you can likely get one top-tier Perk weapon of your choice and then a generic sidearm. Maybe a second tier weapon. But this upgrade will bring your carrying capacity to 20, meaning you can carry two top-tier Perk weapons from different perks with room to spare.
Moving quickly through the others, get Medical Training at level 10 (it's good in all circumstances), get Spontaneous Zed-plosion at level 20 (this will reduce your need to purchase grenades) and get ZED TIME - Lockdown at level 25, as many different weapons have incapacitation methods.
Read more at http://www.gamerevolution.com/features/guide-to-killing-floor-2s-survivalist-perk#ZxI4xyeGs6vf9ZLy.99