no. <br/> or break is like enter so when you open the file there's just empty space which you can not select. while   is like the if you have pressed the space button on your keyboard so if you type <p> </p> it will still look like emty space but you will be able to select part of it with your cursor. Anyway there is no visual difference but things like   are thought to be obsolete and will probably dissapear soon (next 4-5 years)
only if you're a re-re writing idiotic bloated code using some sort of half assed WYSIWYG... P should wrap TEXT, you want a break between your text, that's padding or margin's job in the CSS. I just recently saw a steaming pile of a website for a PHP framework that was doing this type of idiocy: <p>Paragraph about something</p> <p> </p> <p>Another paragraph</p> <p> </p> <p>Another paragraph</p> Code (markup): Rendering the p with no margins/padding and then using the empty P to insert the blank line -- Which is just, sorry to say, rubbish idiotic markup written by someone who doesn't grasp what paragraphs are and/or are for. Of course that same trash website was using P+STRONG to do H2's job, P+NBSP+asterisks to do UL's job, and a whole host of other nonsense that showed the coder in question has no malfing business writing HTML in the first place. P is a perfectly good block level container -- margin it or pad it, don't waste markup on a blank line that your existing P should already be providing you!
Remember HTML is meant to describe content. If you have a piece of text then it should normally be placed within <p> tags. As a general rule I try to avoid using <br> at much as possible. In fact, the only time I seem to use them is when creating contact forms etc.
No <br /> use for line break no extra space up & down <p> </p> it will still look like emty space
<br/> are used to break the line where as <p> </p> Browsers automatically add some space before and after each element.And also <p> </p> will take more space as compare to <br/>
Except that most of the twits and ninnies using the non-breaking space inside the P (pay attention to that   have stripped padding and margins off their paragraphs, which is why said morons seem to think they need that extra markup -- they're using P incorrectly.