They are both very good IM clients with more features than any 
reasonable person could use.  They also have a remarkably similar 
feature set.

I've used both pretty extensively but keep coming back to Kopete.  Why? 
  Because for my purposes, each has one advantage over the other:

o Pidgin handles jabber MUC (conference) rooms much better than Kopete. 
  You cannot 'invite' anybody to a MUC in Kopete, for instance

o Kopete can handle PGP/GPG encrypted messages.  Pidgin cannot

It's the GPG point that seals the deal for me.  I use GPG via IM 
extensively and am not going to go without it.  Yes, I could OTR 
(supported by Pidgin) but that seems a bit too clunky.

Other than that... it's sort of a tossup.

Ryan Rix wrote:
> Hi group,
> 
> I have been a long time user and fan of Pidgin, the multi protocol IM client 
> formerly known as Gaim... However, I found Kopete in Debian's apt 
> repositories just now and it piqued my interest. Has anyone used both and has 
> an opinion on which is better?
> 
> On the one hand I don't want to lose any of the features I've grown to love in 
> KDE, but on the other hand, I'd like the tight integration with KDE that 
> kopete provides (for example showing people's online status in KaddressBook, 
> among others)
> 
> Best,
> Ryan Rix