google keyword planner, should i prefer high or low comp?

hi all
regarding keyword research and which words i should target, in google keyword planner, they tell you if the keyword is low, medium, or high competition. the competition they are talking about is the amount of advertisers competing for that keyword.
so, to me, if the competition is high for a keyword among advertisers, it would seem that that would be because the keyword itself was too hard to rank for through SEO. so then if keyword planner says low comp among advertisers, that would indicate the keyword is easier to rank for so theres not as many people spending money on ads.
if this line of thinking is correct, then when using keyword planner to research keywords, i should be looking for keywords with low competition, correct? or is this thinking incorrect?

i realize i think that google keyword planner competition level is a different thing than what i might see when researching the difficulty to rank a keyword using something like market samurai. google keyword planner is talking about the competition among advertisers, market samurai shows me how strong the SEO competition is, right?

(assume i am using nothing but google tools)

thanks in advance for any input