In my experience, trimming is the process of cutting out the margins around the images.
Edging is the process of applying ink to the edge of the card (not to the image, but to the external perpendicular half a milimeter edge of the cardstock - exactly where the card would be gilded with gold leaf).
Reasons for trimming include :
- making the cards smaller and easier to handle
- removing borders that you do not like (either because they are uneven, or because you find them ugly, or because they have signs of wear and tear)
- making the image "pop" more by getting rid of a white margin
Reasons for edging include :
- covering signs of wear (especially on cards which have a dark border)
- giving the deck a more wholesome look by matching the edge of the deck to the color of the back
- adding a touch of bright color to the edge of the deck
- making a deck more elegant by getting rid of the whiteness of the edges (especially for decks with dark borders)
I am not a compulsive trimmer but I have trimmed a few decks, amongst which my Tarot of the Druids (Druidcraft) to make it manageable. The cards were so large as to be "unshuffleable" and I never used it as it were. Plus, it looks much better, more vivid now that the borders are gone, but that is my personal opinion.
I also agree with people who find that nice borders can add beauty to a deck, but that ugly borders can kill the look of an otherwise pretty deck. Especially borders with titles of cards in 100 languages IMO (Yes I am looking at you italian company with a beetle name)
So I have trimmed a few decks just to get rid of borders that were anoying me so much that I was not using the decks at all (tarot of the Magical Forest for example)
Finally, I have trimmed a few decks "just because I could" and to have a version of the images with popping vivid colors. For example, I have two copies of the Albano Waite, and I trimmed one. It does change the look of the cards, and make them appear more vivid. I would not say the trimmed version is better or worse than the original version, it is just different and I like it a lot.
Following that idea, I am planning to trimm my Centenial Smith Waite, and I am considering trimming my Japaridze.
I prefer to trimm with a good pair of scissors with long sharp blades. I find that the result is better, because in my experience the use of razor knife can "pull" on the card a little, creating ridges and hurting the lamination. Of course that depends on the knife and on the carstock quality. But, with sharp scissors, I find that I obtain a very smooth edge, and that it "closes" the lamination on the edge (I do not know if I am clear)
Plus, with experience I find it easier to make a straight cut exactly where I want it to be, with scissors than with a knife or massicot (I thought it would be the other way around, but in the end I find the scissors easier)
Rounding the corners with a good corner clipper will finish the job, gives the deck an even look, and prevents sharp corners that will hurt your hands and wear off faster than the rest of the deck.
The first time I did it I was nervous, but it turned out so beautiful and so even, that it encouradged me to do it again. It is especially important to know that you can obtain very even sides that look professionaly done, if you go slowly and carefuly about it.
I take my time, one card at a time, very carefuly, and I obtain extremely even decks that way. Trimming a deck that way will take several hours.
I love gilded decks, because I like the edge of the deck to look good. But gilded decks are rare, so, edging a "nude" deck with ink is a good solution for me.
I have edged decks that have dark or black borders to give them a classy look (Magical Realist deck with black ink ; Gothic tarot with red ink, Anna K with yellow ink...) and I have edged decks to cover signs of wear (Tarot of the Trees with green ink to make up for the terrible cardstock quality).
I have also edged borderless decks just to give them a more wholesome look (my trimmed Druidcraft is edged in green, my Bohemian Gothic tarot is edged in soft blue grey....)
Edging should only be done to decks that have a cardstock that can take it. Plastiquy cardstock will not take the ink at all, and the risk is that the ink will go everywhere on the card but on the edge, thus potentially damaging the deck.
Papery cardstock are better edged with ink that dries super fast, otherwise the wet ink can travel under the lamination, and create a halo of ink all around the border.
Personnaly I avoid edging decks that have a white border, because I find that the risk of ink running is too great, and the finished look will not be professional, but that is just my personal experience.
All this is personnal and I understand that some people will never touch a deck with scissors or ink.
In my personal experience, trimming and edging a deck is something I do as a treat to myself and the deck, and it strengthens my bond with the deck. Like sewing a nice bag for the deck, or adding a decoration to the deck's box.
Most decks I do not touch with scissors or ink because they are perfect as it is, but for some decks, it is a fun plus.... and in some cases it has even enabled me to eventually use a deck that was otherwise sleeping untouched on the bottom of my tarot box (the tarot of the Magical Fores : I love it so much more now that I rid it of its borders....)
You will find numerous images on internet showing trimmed and/or edged decks, and you can see if for you it adds beauty to the deck, or if on the contrary it "butchers" the deck. That is very personal !