I’ve been using block heaters for over thirty years and I would definetly install it in the block. Hose heater do work pretty well but a block heater is more effiecient at getting the block warm. Yes they are little more difficult to put in but you said you had a mechanic to do the work for you, so it will cost a little bit more but I am sure your mechanic can handle it and it will be money well spent. Good luck with your decision, either way they both help the block heater just helps more. If it matters I was a mechanic for GM at one time.