If what you want is a quotation or offer, then sending a letter of intent makes you look ignorant while requesting a quotation will generally at least make you look like you know what it is that you want. And what you want, after all, is a price quote. Hence you want to request a price quote, via a request for quotation.
"Letters of intent are often touted as a 'non_legally binding' way to get the parties to set forth in writing what the undertaking is among them relative to a transaction. Too often, parties will sign such a document, feeling that they have little or nothing to lose by doing so... [True, that's] one of the attractive elements of the letter of intent [its purported non_binding nature]. However, courts have found letters of intent to create binding obligations, even if the letter itself does not explicitly state that it is binding... certain provisions within the document may indeed [still] have legal effect."