The Conda is the sensible choice for a lot of roles but the T10 is simply more fun, a wingmate build one with 9 missile launchers (Packhounds in a few weeks) and it's a ludicrous monster in a HazRES or pirate threat zone.
Both the Conda and T10 have terrible SC handling so...........
I really like the t10 (visually) but its not a very good ship. The Anaconda, using a class 6 shield, has better shield capacity than a T10 using a class 8 one. So if you don't need shields for anything other than occasionally bumping into something, then the t10 can be okay. For fighting, the hardpoints on the Defender are really, really far apart and i have yet to find a useful loadout with turrets of gimballs that is even remotely acceptable for me.
On the positive side the t10 has good sounds, nice visuals and an awesome cockpit. It just happens to perform worse at pretty much all tasks compared to other ships.
I can't add much to what others say but I've had both; I flew a Conda for about 1.5 years and enjoyed what it brings to the table, long jump range and big cargo. I did not like combat in the conda so I ended up selling it to buy a T10. I really like the T10. My main ship for about 2 years was a T9; made me lots of credits way back in the early days so I'm used to the SC handling.
My T10 is an armored trader/ low capacity passenger ship. I really like it. Its my big combat ship now. It has the largest re-buy of all my ships but I haven't had to do a re-buy yet plus I've won many bounties due to its combat abilities.