I'm looking for a holdout that I can wear all day at work for some casual magic when the time is right.
Since I'm always wearing a shirt at work, my first guess was that the TKO 2.0 would be perfect. However, since I'm most of the time sitting down I was wondering if the TKO isn't too bulky and makes the shirt look funny? It should also be noted that I keep my shirt tucked in all the time, and that I'm a relatively skinny person.
While looking into the subject, I have found some reviews that said the UCCU is more invisible but less versatile, so I was wondering which one I would be better off getting?

They both operate the same way. Neither having your shirt tucked in, or being skinny should be an issue. As long as it's a button shirt, you should be good. I have both, my TKO is white, and my UCCU is black.

It comes down to what you prefer to perform. The UCCU is ideal for card magic, as it's been specifically designed for it, you technically can do other stuff with it (like coin magic) but it's not ideal.

TKO 2.0 is perfect for coin magic. I haven't used it for cards, so I'm not sure whether it's on par. Come to think of it, I got both second hand so I don't actually know if I have 2.0 or the original. If I remember correctly, TKO 2.0 was meant to incorporate some of the UCCU stuff, to make card work, workable.

IIRC, TKO 2.0 requires a modification to the shirt. Someone please correct me if I'm misremembering this. If you're just going to be doing card work, then I'd recommend UCCU because it can be easily added/removed from any shirt at a moment's notice.

If you're interested, I've got a method where you can achieve the same result without the UCCU, and will work with nearly any button down shirt. PM for details.

Thank you both for your comments! There was a sale going on at my local magic shop, and I decided to take the risk and order both the UCCU and TKO 2.0 (UCCU was only 10 euro's!). Once I receive them I'll post again to say which one is best for everyday use.

I hadn't realised that UCCU still existed in its own right. I thought TKO had superceded it. I use TKO to vanish a phone and have played with it for cards across. The need to slightly modify a shirt is a bother so armed with the info from this thread I have ordered a UCCU - if there is only a small advantage over TKO for card work then it will be worth it