Hello, today I have several doubts, so I am publishing them before I forget them.
A few years ago I bought the Fairphone 2 and when I picked it up with my hands I did not like the feeling it gave me. It’s a very big phone, heavy and with a lot of frames.
Will Librem 5 be physically better?
It will only be possible for you to know this when you are holding it in your hands. 
I like my Fairphone 2 very much.
Personally, I like heavier phones. Thin phones with glossy back slip easily from my hand. And heavier phone is easier to repair and upgrade. My phone is a productivity tools, not a fashion gadget. 
As someone who just recently got a FP2 I feel like I need to point out the obvious here:
The FP2 is big because of its modular nature. It is designed to be repairable. This increases the bulk of the phone as they use standard screw and bolts, and have to make accommodation for user removable batteries, etc.
Have you seen the mockups of the L5? I do think it will be a tad smaller than the FP2 but it is going for similar repair abilities points here.
It will be glorious because of this, not in spite of it.
I made some estimations based on the design renderings and the 5.7" screen size. You can find it here: Size comparison to other phones
Also the librem 5 will be ~14mm thick which is 3mm more than the Fairphone2.
And i think the librem 5 will have a metal back which tends to be heavier than plastic.
From my point of view the librem 5 will be a big heavy phablet and that is for me to much of a compromise to do the jump form my iphone 5 to the L5.
But i think that is the thing with libre and privacy, often it still is a big compromise, which not so many people are willing to do, but purism is doing really great in making it less and less an issue, while the big companies are increasing the pressure to go away form them.
It’s just the question how annoyed you are already and how much you are willing to compromise to escape.