I think that a personal trip would be of much benefit to both you, your stuff and your client. It is always nice to touch base with people personally and leaves a much better impression.
Also it is a bit of piece of mind too as the item(s can be handed over totally undamaged. You do not want your build kicked around a depot as they will when labeled as fragile etc.
It also gives you the opportunity to visit somewhere, time away from the bench etc is never time wasted as you can plan in a visit etc. Don't rush the trip and enjoy the ride. Plan for an overnight somewhere nice rathre than those horrible motels I have heard about and seen on American movies and TV series.
Take the time for a personal visit and maybe factor some costs into the build costs for your client!
Quite a will ago I ended up building this for a friend of a friend in Hamburg, Germany.
http://www.jotika-ltd.com/Pages/1024768/Nelson_12.htm
Rather than send it by carrier I decided that I would go on a visit to my friend in Germany (The Hamburg Harbour Celebration was close and lots of fun) and take it with me.
I asked the airline if it would be possible to take this into the cabin with me as it was delicate. I was told to ask at the airport at checking in time and so I did. There was some confusion so I asked if I could see the captain and ask permission, taking the case and ship out of the box I had made for carrying it. Eyes blinked at the build, the pilot came, looked, and said that it would be fine on board and would make room in crew stowage.
I had to change aircraft at Amsterdam and the Pilot spoke with the other pilot of the plane going to Hamburg from Amsterdam, also I got a ride through the airport in one of those little buggies.
The victory ended up in Hamburg without a dent, or broken rigging etc. The client was delighted, I had a great time at the Harbour fest and as a thank you I built these for the Airline which sits in the crew room/office at my local Airport and Amsterdam.
http://www.jotika-ltd.com/Pages/1024768/Nelson_5.htm