Which is More Damaging: Heat or Relaxers

I've been trying to let my hair go longer without resorting to relaxers on my new growth.  I've become a product junkie after lurking on this forum even more than I already was before.  LOL  I've been using Cream of Nature shampoo, Salerm, a heat activated conditioner periodically, and as soon as it arrives, I'll add ORS to my arsenal to battle my bad hair.    I've noticed that the shedding/breakage has stopped now that I have started taking better care of my hair and not neglecting it by putting products in it that tended to dry it out.  Certainly, I've noticed that my hair is fuller and I there's been a bit of growth since I started all this in May. 

My question is it too damaging to use a flat iron if I'm using a heat protectant versus putting chemicals on my hair?  Is it further damaging to my hair to use a ceramic flat iron on the relaxed growth even if I'm using a good heat protectant and the temperature isn't too high?  Finally, is flat iron use less harmful (even on relaxed hair) than trying to blow dry it straight?

   Ok heres my opinion on this Firstly I use
relaxing my hair lightly and i use heat on it and with
the proper conditioners and products my hair
GLOWS but that may be just my specific hair.. I think
chemicals are worse than heat but only worse than
heat in moderation,, too much heat can just burn
your hair right off,,hair is still healthier if it not
relaxed,, relaxer just damages the hair becuz thats
how it works its magic,, i think that hair is stronger if
not chemiclly altered,, so if u can get away with just
heat in moderation(not too often,not too high temps)
then try it:-) good luck

Both can be damaging but I think relaxing would be more damaging than flat ironing.  And, blow drying to get the straight look is more damaging than flat ironing.  I hardly ever blow dry and only flat iron once every 2 weeks.  Your hair will be much more healthy if left natural and if you don't put relaxers or heat on it (or limit heat use), it will grow even more.

I think it depends on your texture (thin, medium, thick) or hair type (1-4)

With all if you have a relaxer then avoid heat as much as possible only flat iron right after you have washed and deep condtioned your hair(don't do it on dirty hair).  But flat ironing should be used to help extend your relaxer so wait until about 5-6 weeks after you relax before you start.

As far as which is the lesser of the evils each has it draw backs: