I have worn glasses for 30 odd years. I have had large lenses (fashionable for a long time) and in recent years smaller lenses. It is a very personal choice but for what it is worth here are my views!
My last two pairs have been made from titanium.
Air Titanium and now
Silhouette
The advantages of the above makes are twofold, titanium is ultra light and very flexible and neither make use screws. If I wear one of my old pairs now I wonder how I ever got used to the weight!
Rimless or thin rims are probably better for flying due to the lack of obstruction to your peripheral vision, certainly I like my rimless pair for that very reason.
I have just, for the first time, had to have varifocals. I suffer from astigmatism (oval eyeballs basically) meaning I need correction for both long and short vision and now I have reached the age where my arms are too short so need reading correction as well. I put the decision off for two years and struggled with reading, especially at night, purely because I had heard horror stories about distortion and difficulty in adapting.
I have regularly heard that cheap varifocals tend to give more distortion and that they are to be avoided. Essilor invented the varifocal and their latest lens,
the Panamic lens, is what I now have. I collected them with some trepidation and have been truly amazed. I put them on and drove home as if I had been wearing them for years. The reading area is small and I am unaware of any distortion. The movement of the head to focus on print or instruments is small and comes naturally very quickly. The only time I can make myself aware of the fact they are varifocals is looking straight ahead and then glancing down at the ground without looking down, I am then looking long distance through the reading section. In my case not a problem or even that noticeable but in helicopters it might be a factor.
From an aesthetic point of view you will see referral made to 'Index'. A high index lens is thin for a given refractive power compared to a low index lens. My early large lens' were not that strong but due to the curvature of the lens looked very thick. I now only have high index lens (some of the latest are over 1.6) and they avoid the 'bottle top' appearance.
Finally, the mark up on glasses in the UK is a disgrace. My current pair cost me £450. Glasses are now becoming available at greatly reuced prices via mail order. I would not personally buy variofocals this way because the precise location of the finished lens in relation to the wearer's eyes is critical. Similarly if buying abroad taking them back is more difficult although great savings can be made. A simple prescription gives more scope to shop around.
A small trustworthy optician would be my choice rather than a large chain. I use one in Hertfordshire and will supply his name if anybody wants by PM.
Sorry for the lengthy post and good luck!
PS I have no connection with any of the companies in the links above.