Well, your first challenge will be to find a 10D, and even then you won't improve that much in size and weight over the 1D. Your next challenge will be to find a Pro 1, but if you do manage to get your hands on one it will bring a big weight and size advantage over your 1D or a 10D.
Since each camera has its own usage realm, the main question is what you want to shoot on your trip. The 1D and 10D will have speed and ISO advantages while the Pro 1 is undoubtably a compact power package that gives sharp pix, 8 MP cropping options and versatility. It is not a low light wonder, so you will have to do the usual work arounds. I have only had mine since Tuesday, but I already know it's head and shoulders over a G3 or G5. I find it's performance quick, efficient and a pleasure. The kind of camera I would like to have with me anywhere.
Germany and CZ are rather gray and rainy this time of year, so light isn't so bright and pretty diffused, so light will be a factor for you. You can always bring two cameras and leave one in the hotel depending on the weather. But I would want a Pro 1 in any case.