Travel camera

Let's consider the major decisions first. You are going to buy into a system with future potential and are trying to work out the criteria on which to make it. You mentioned possible image quality advantage of the larger sensors compared with the m43.

In fact, I think the difference in quality are a very minor consideration. Any of the comparative tests will be fussing over pixel-peeping at noise levels at high ISO settings. Don't be distracted by that. It shouldn't really even come into consideration because it's such a minor factor.

In my opinion, the only important difference is system size. Your entire system is going to be much smaller and lighter using m43.

Next, you said you used the view finder on your dad's camera but are unsure about EVF. The newer types of EVF as used on the E-M10 is not only adequate, it has some significant benefits, such as magnification. It is better in low light and I would choose it over my old OVR anytime.

As for night shots, again the E-M10 also has a very interesting composite mode that builds the image up. And on a related note, Prime lenses are not just for the sake of artistic purity. They give you a very real and useful advantage over zooms lenses in low light.

For indoor, dusk, inside caves or dark forest, you will be able to hand hold in so many more situations before having to reach for the tripod. And they are usually the moments that you just don't have time to fuss with tripods. I suggest to get at least one standard focal length fast prime (probably 20mm or maybe 25mm)...but then, I like primes and I don't mind having to change lenses, so I am biased.

You have to choose whether you prefer lighting flexibility and range (primes) or compositional convenience (zoom).