Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate YI M1 and Olympus PEN-F side-by-side from the front, back and top in their relative dimensions. 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). Olympus PEN-F has external dimensions of 125 x 72 x 37 mm (4.92 x 2.83 x 1.46″) and weighs 427 g (0.94 lb / 15.06 oz) (including batteries).
Below you can see the front view size comparison of YI M1 and Olympus PEN-F. YI M1 is clearly the smaller of the two cameras. Its body is 11mm narrower, 8mm shorter and 3mm thinner than Olympus PEN-F.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
YI M1 is significantly lighter (77g ) than the Olympus PEN-F which may become a big advantage especially on long walking trips.
Also keep in mind that body weight is not the only deciding factor when comparing two interchangeable camera bodies, you have to also take into account the lenses that you will be using with these bodies. Since both YI M1 and Olympus PEN-F have the same Micro Four Thirds lens mount and Four Thirds sized sensors, lenses will not be a differentiator on total size of the system.
Unfortunately neither YI M1 nor Olympus PEN-F provides any type of weather sealing in their body, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
YI M1 and Olympus PEN-F's LCD screens has the same diagonal size of 3".
On the other hand, Olympus PEN-F sports a Fully Articulated screen
which you can change the angle and position of the screen almost freely, making it possible to shoot from waist or over the head levels, and especially very useful for shooting selfies and video. YI M1's LCD screen is a fixed type which provides almost no flexibility in shooting positions compared to PEN-F.