Helbindi +res or +def

Hi,
I have 2 Helbindi which have +res/-spd and +def/-spd and I intent to use him as a green strong wall unit like Dorcas.
I would choose the +res/-spd in order to survive against strong blue mage and some green mage. But I wonder if +res wouldn't be too much and +def should be much better...

Should I choose my first choice and go for the +res or choose the +def and maybe survive against some swordman ?