Pozdrav
You are looking at two different instruments for different purpose. The real question is what do you need.
Fluke si portable, has higher CAT ratings etc.
Keysight U3401A on the other hand is designed to be used in the lab (low energy stuff), like all bench multimeters. It has lower CAT ratings, and you don't have to worry about battery because it's mains powered. Display is also easily readable both in the dark, and on the light.
U3401A is the basic bench multimeter so there is a lot missing features. It even don't have 4 wire resistance measurment.
I would probably go for the Fluke, or similar HQ hand multimeter, and if there is need in the future, then I would buy "real" bench multimeter with all main features.
There isn't anything worth paying 25% tax on.
By tax he ment VAT. VAT in Croatia is 25% and you can avoid it.
It should also be noted that Fluke's "lifetime" warranty is actually something like "As long as we sell this model or ten years, whichever is greater" (don't quote me on the details).
Lifetime warranty isn't really lifetime warranty.
Also there is something different about US, and other countries if I recall correctly. You (mzdenkov) should check that.
But that wouldn't worry me. Nor is 3 year Keysight warranty something crucial. These are high quality and tested devices, and if they fail in the warranty period that will probably be user error. Of course, some production defect are possible, but highly unlikely.