The "Victorinox Compact" is the lightest SAK which has attached every tool you need on longer trekking tours.
What you need is attached, what you wouldn't use is missing.
This SAK is constructed especially for longer trekking tours. Useful for every travel, but made for trekking tours with modern stuff.
It is UK legal.
The Victorinox Climber is heavier, but cheaper. If you compare them directly, you see, that the Compact is worth the money. It is a bit better thought through, let's say it is the younger version of the Climber.
You nearly never need a ball pentel if you are on a trekking tour. It is heavy to store a ball pentel so that it cant break. If you have to write, people will give you a ball pentel.
But if you should need an one ball pentel, you have a very small and light one in the Victorinox Compact.
The same with scissors and blister needle.
You pay some coins more, but that saves weight in the ruck sack, because needle and scissors don't need to be stored with an extra (heavy, stressy and expensive) package.
For ultra light pegs sometimes you need the peg hook. The Compact has a nail file at the hook, most others have the hook but not the file on it's back. In this details you find the reason for the higher price of the Compact.
The bottle opener of the Compact can be used as a tin opener. Now a days most tins do not need a tin opener, so this opener is working well enough. The tin opener of the Climber works far better, but the tin opener of the Compact works really well enough if you need it ones a month.
I recommend to spend the bit extra money and to save volume and weight in the pocket and to take the few more tools the lighter Compact offers!
Yes, the Compact offers more tools, than the Climber, if you compare it well!
Should you not need this knife, should you just want a single blade for day hikes, I recommend the Opinel Carbone No7, because it is incredibly light and very cheap, and with a bit modification of the handle you will get it even lighter.
You can easily get it razor sharp, far sharper than it is delivered, and you can easily shorten it's 7,7cm blade a bit to make it UK legal to carry. If you close the knife and lock the blade with the ring and open it with pliers, the locking ring will fly away. You could put the ring in the ruck sack and the knife in the pocket. To press the ring back, you don't need any tools.
The handle of the 7 is a bit short for adult men, but if you do not plan to make a lot of wooden pegs every day, that knife is OK.
It's incredibly good for carving and to use it in the kitchen.
Should you want to produce a lot of pegs, hundreds of pegs every day, the No8 would be the right size. The handle is constructed for glove size 10, what means for adult men. The No8 nearly can replace a fixe bladed knife with it's incredibly sharp 8,5 cm blade.
So for breakfast and kitchen and wood carving from time to time the 7 is the lighter, legal option, for bushcraft the 8 is the better option.
If you want it for hiking and climbing, you should understand, that the Opinel 7 and 8 are perhaps the lightest knifes in this sizes!
You will get the Opinel Carbone versions sharper than the inox versions.
SAK and Opinel are perhaps the most sold pocket knifes of European production and there are reasons for it.