SEO is speculative at best.
As a rule, the accepted agreement is to use where necessary, and you will not suffer. For example, I would write your code something like this:
<div id="hdr-top-logo"> <h1> <a href="/" title="Blahblah.com logo"> <img src="logo.jpg" alt="Blahblah logo" /> </a> </h1> </div>
The benefits of using text instead of a logo will not be significant.
Note: alt + title should be descriptive , so donโt just enter a bunch of keywords, otherwise you will suffer from SEO.
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