Hi,
The amount space looks the same on my screen for both the first two links.
The second however isn't anything to do with the plugin as far as i can tell, i don't output any spans or breaks for the tabs, and only paragraphs inside the tabs.
Screenshot of mysterious paragraphs with span and breaks
http://img818.imageshack.us/img818/4931/topic6982.jpg
My plugin's code, specifically the two functions that produce HTML output for the tabs.
http://plugins.trac.wordpress.org/browser/put/trunk/put.php#L355
http://plugins.trac.wordpress.org/browser/put/trunk/put.php#L358
I'd have to guess/assume this is something to do with what you're putting into the editor, and/or something another plugin you have installed is adding.
Could you create a test post and put the following in the editor please.
Line of text 1
[tab name="Tab name 1"]Tab 1[/tab]
[tab name="Tab name 2"]Tab 2[/tab]
[end_tabset]
Line of text 2
Save it, and provide a link to the test post please.