Ohh thank you for asking this. Following! 😛

The main advantage of custom glass doors is 'framelessness.' Off the shelf glass door kits have aluminum frames, channels, rails, hinges, sliders and whatnot which detracts from the clean, minimalistic look you get with custom.

Thank you @Home Reborn. But I’m seeing many “frameless” options at places like Home Depot. Here’s one example - is there a different level of “frameless-ness” that Custom offers? I’m also looking at only 3/8” thickness

It might also be the different types of finishing. For glass doors, you might also want the added protection in case the glass breaks, there is an added process that the glass doesn't shatter, but stays together or breaks into like pebbles versus huge shards of glass which could be dangerous. Not sure if the HD variety has that included. Aside from that, there is probably not much difference.

The issue with that particular door is the incredibly narrow range of shower alcoves it will fit: only from 48" to 48 3/8" wide. The entire shower alcove would have to be incredibly carefully constructed so as to ensure that the alcove width - with tile backer board, plus waterproofing membrane, plus thinset, plus tile - would "land" in that super narrow range. Plus the walls on both sides would seed to be absolutely prefectly straight and plumb. All of which borders on the impossible!

When you get custom doors made, they compensate for all those variables so you have so much less to worry about. That's why most prefab glass door kits have all those adjustable aluminum channels, overlapping door panels and whatnot: to allow the glass panels to fit a wider range or shower alcoves that are not perfectly constucted.

"there is an added process that the glass doesn't shatter, but stays together or breaks into like pebbles versus huge shards of glass which could be dangerous."

That would be tempered glass and is 100% code for every shower enclosure, prefab or not.

@Home Reborn Thank you so much. So for a hinged door, it definitely makes sense to go custom. What if I change it to a sliding door (where there's more flexibility in terms of width)? And the other bathroom is just a panel wall (doorless, curbless shower). In those two cases, would you still recommend Custom vs Prefab? Really appreciate your answers!

including one example of each type of door:

https://www.homedepot.com/p/VIGO-Elan-Cass-44-to-48-in-W-x-76-in-H-Sliding-Frameless-Shower-Door-in-Matte-Black-with-Clear-Glass-VG6044MBCL4876/316291267

https://www.homedepot.com/p/Glass-Warehouse-49-in-x-78-in-Frameless-Fixed-Shower-Door-in-Matte-Black-without-Handle-GW-SFP-49-MB/308178047

Try to keep DIY shower door projects small as its an expensive & unforgiving project to learn on. We use 100% custom enclosures on custom homes. We use prefab standard enclosures on small openings at flips.

Glass gets heavier with thickness. The one piece you linked weighs 140 lbs. That's not a novice one person install.

Expert measure, built to size, install and warranty costs more and adds value.

To add to what Jeffrey says, you also do not want to have to drill tile twice as it is typically not very forgiving.

@Lana Ho - Yes, a sliding door system will cope better with minor construction imperfections, as the doors can overlap by whatever amount necessary.

Another consideration you might not have considered: Any custom glass company's quote is going to include installation cost (as it is a specialty trade). But who's paying for the installation of these Home Depot units you're considering? If you're a DIYer, sure, you will save some money. But if you're paying a contractor to install it and he's not familar with the product, it could take the better part of a day to do the install. (And at my rates, it isn't much of a leap to go custom!).

Have you considered a shower curtain? It's a whole lot less expensive than a shower door (even if you're not going custom), and it excuses you from keeping the glass clean, which is a constant job.

We went with a shower curtain in our master bath when we re-did the shower, and I'm not missing the glass doors at all.

@Home Reborn yes, I would be paying my GC to install it and I think they normally have the Shower door company do the install so that is a consideration. Also, the glass company will provide a warranty that I won't get with the prefab. Really appreciate all the insight!

I guess it's obvious, but with custom you can pick the exact size you want the door and fixed glass panel to be, choose how door swings, choose handle size, style, finish, etc.