I have converted 4 bikes from mechanical to electronic shifting and I bought one set up for Di2 and converted it to eTap and sold the Di2 parts. I'm a big fan of electronic shifting and I'm sure you'll like it. Took me a while to edge up to the decision until I finally went through with it so I get where you're coming from on this. Once I did, I loved it and that was that. eTap installation is super easy and super clean without any derailleur wires. You can do it yourself in an hour or less without ever having done it before.

With the conversion, how do you know what to order?

Research, research and more.

If you can keep the crank, chain and cassette, as well as rim brakes, you save on not needing those parts. So you then need shifters, front and rear derailer, A and B junction boxes, battery and a holder if internal in the seatpost, 6 or 7 cables of correct lengths. Maybe hydro cables and brake units if doing disk, plus the knowledge and tools to install a hydraulic brake system.

Lot's of YouTube videos on how, it generally really simple.

I got a partial kit from Texas Cyclesport. When you buy the kit they ask you to specify easy stuff like braze-on or clamped derailer, Regular or longer cage rear derailer, battery charger (yes you need it), and cable lengths, which you can easily ,measure using a piece of srting and then just order a bit longer, the cables can hide away.

And a PC laptop to run the E-Tube software for easy system configuration, you can also do it via BT and an iPhone/Pad, if you purchased the BT unit.

I have Dura Ace mechanical on my trainer bike and it shifts great. I don’t mind it at all. Of course the bike is never out in the weather and I only spend a couple hours on it at a time. Fabian Cancellara preferred mechanical over Di2. Of course the cables were probably replaced every week. I feel the real advantage of electronic shifting is not that it shifts better, but has zero maintenance to maintain that optimum performance.

The hoods are quite different as well on GRX

I'm not sure I totally understand your question. With the Red eTap (older version of eTap), you just had to make sure you were set up for the FD mounting on the seat tube. Other than that, I could see no reason to not get the WiFli version with the longer cage which gave a wider choice of cassettes.

My wife has AXS on her new gravel bike, that was a little different. You basically need to decide what you want in terms of drivetrain generalities and then buy components that work from there. All the parts are compatible between all the AXS compatible shifters and derailleurs for both mtb and road components. In point of fact, she has a 1X system with a 44T chainring on front and the 10-50 cassette on the back with the mtb RD. Works great and gives her an extra gear lower than her prior 50/34 with a 11-32 for when we ride in the mountains. But, other than that, it's pretty straightforward. Decide which brakes have so you get the right brifters, the chainrings you want and the cassette choice. We went with Force on her bike, she rides less than do I but other than a marginal increase in component weight, it seems to work pretty much the same as the top end stuff.

J.

I upgraded from 6800 to 8050. I bought the full groupset from Bike24 in a black Friday sale for €940 shipped. I stripped the 6800 from the bike and sold it for €330. I fitted the Di2 groupset myself so cost of upgrade was €640 (less than $700) Totally worth it!

I would absolutely and totally upgrade the bike to Di2. I've had electronic shifting on my TT bike since 2014 or thereabouts, but i only recently put it on my road bike. And after that, i cant go back to mechanical.

If you are buying the Di2 locally, perhaps the shop where you are buying it from can throw in an install for free - worth asking.