Size and weight are big decision factors when you are trying to find the ideal camera for your needs.
In this section, we are going to illustrate the Pentax RZ18 and YI M1 side-by-side from the front, back and top in their relative dimensions. Pentax RZ18 has external dimensions of 97 x 61 x 33 mm (3.82 x 2.4 x 1.3″) and weighs 178 g (0.39 lb / 6.28 oz) (including batteries). YI M1 has external dimensions of 114 x 64 x 34 mm (4.49 x 2.52 x 1.34″) and weighs 350 (including batteries).
Below you can see the front-view size comparison of the Pentax RZ18 and the YI M1. Pentax RZ18 is clearly the smaller of the two cameras. Its body is 17mm narrower, 3mm shorter and 1mm thinner than YI M1. As you can tell, actually this is not a fair size comparison since Pentax RZ18 has a built-in lens but YI M1 doesn't. Once you put a lens on M1, its thickness will increase significantly.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
YI M1 is 178g lighter than the Pentax RZ18 but we don't think this will make a significant difference.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on M1, the total kit will weigh much higher.
Weather Sealing
With its weather-sealed body, we believe that the RZ18 has a big advantage over the M1 which doesn't provide any kind of environmental sealing.
LCD Screen Size and Features
Pentax RZ18 and YI M1's LCD screens have the same diagonal size of 3.00 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.