A good porro prism from Nikon, bushnell, Steiner, etc. The Roof prisms are good but they are more expensive. Your best bang for the buck will come out of a pair of porro prisoms.
Not knocking the 10x42 but if light gathering ability is key, the 8x42's will get you a better exit pupil. If you are set on the 10 power then you would have to get into the 50mm objective to get the same light gathering ability as a pair of 8x42's. The 8 power will stabilize better giving you a clearer field of view.
The exit pupil is the bright circle that can be seen in the center of each eyepiece when you hold the binoculars about 30cm away from your eyes with the objective lenses pointed toward a bright light. The larger the diameter is, the brighter the viewfield is, which is an important consideration when using binoculars in darker situations.
Exit pupil = The effective diameter of the objective lens ÷ Magnification
With 8x42 binoculars, the formula is 42 ÷ 8 = 5.3.
Therefore, the diameter of the exit pupil is 5.3mm.
This figure indicates the brightness of the image in view.
The 10x42 has an exit pupil of 4.2.