That is a hard choice to make
Glock advantages
Lighter weight
More choices in calibers and frame sizes
Cheaper initial purchase price
Simple basic durable tool
Smooth lines aid in CCW
Less likely to worry about getting in banged up or scratched (combat tupperware
)
Low hand to bore axis means less felt recoil
Fast and short trigger reset
Very few parts a simple proven design
Very durable finish and polymer which does well in a harsh or wet climate
Glock disadvantages
Factory sights can break and the front factory sight can come off once it has been banged or dropped!
No second strike if you have a bad primer strike
Not always the safest choice for semi skilled or unskilled shooters
You must dry fire the pistol to field strip it
Barrel rifling type does not allow lead reloads and factory does not recommend
handloads
The plastic recoil spring guide rod can break as can the trigger spring, it rarely happens but I have seen it a couple of times
Sig Advantages
Among THE best pistols currently made top quality materials and craftsmanship
You can choose from double action/single action to double action only.
Very good proven designs (very few disgruntled Sig owners)
Good ergonomics
Simple to use and train with
Simple and safe to take down with no need to dry fire
Has a decocker should you need it
Usually more accurate than a Glock
One can use different grips with it as well as the short trigger if one has small hands
Sights are allot more secure with dovetail mounting front and rear, the Glock front sights can come of and the adjustable factory rear sights can break.
More people feel pride of ownership in owning a Sig than a Glock as Glocks are seen more as tools.
Higher resale value if that is a concern
With a light primer strike you can have the option to pull the trigger again something the striker fired Glock can't do.
Sig disadvantages
Higher initial cost
More weight in comparable models
Not as smooth lines more edges and corners
A bit thicker than a Glock since the Glock does not have grip panels
Higher slide to hand ratio for some it seems to recoil a little more
Can be harder to find new or used as they are less common and people seem to keep them for some strange reason or another.
These are my observations and opinions others will have their own, either one is a good choice pick the one that feels and works best for you rent beg or borrow one of each and buy a few boxes of ammo and ring them out and see which you like.
Best of luck.