train or plane odessa or warsaw to tblisi?

Odessa. If you go there you won't want to leave. Its beautiful.

I should have addressed the travel part of your question. Trains are a possible choice, but not from outside Ukraine. Flying is different, but that depends where you are flying from. I suspect you will be landing some where in western Europe first. The airline you might look at is Aerosvit and they have a web page. I think they fly from several places in America. Fly if you can. Trains, although good, are a different proposition than in western Europe. We took one from Cherivsti to Odessa, overnight, nineteen and a half hours, comfy, but utilitarian. So I would suggest flying into Odessa, spending a few days there then going on to Tbilsi. I can heop with an excellent hotel in Odessa if you wish.

Many years ago I was in Tbilisi. My educated guess would be that easiest connection you can find via Moscow. If you can, fly. Train takes forever. I flew from Moscow to Baku and then train and it took all night and then some. Look at the map and it seems that Baku and Tbilisi are close.

You need to do some more research. I don't even think that train is an option - if you look at the map, from Odessa you would either need to cross the Black Sea on a boat possibly to Batumi or would have to go through Russia. I seem to recall that the border crossings between Georgia and Russia were not open to foreigners or at least most nationalities(this was 2 years ago) - though it did seem like I saw a lot of Poles riding their motorcycles down around Kazbegi (this is about 10 miles from the Russian border). 2 years ago I took the LOT flight from Warsaw to Tbilisi and back. It was straight forward and took about 4 hrs each way. For me, this was just a continuation of a frequent flyer ticket from the US and I took a 5 day stopover in Poland. I am not sure that Odessa is going to be much of an option if your final destination is Tbilisi. I would recommend you book a through ticket from the US and try and break your journey somewhere in Europe (but try and do it all on one ticket). If not, search on Kayak or some other engine for ticket prices between Warsaw and Tbilisi. Another alternative is to consider Turkish airlines via Istanbul. You could also do some searching on the Thorntree forum for other options.

Many thanks for the extremely helpful replies. WE will be returning via Turkey, so I was wanting to break up the destination flight somehow in a different direction. Thanks again for your responses.

Train isn't really an option with Georgia (unless you travel from Baku or Yerevan), however from Ukraine there a number of option how you can reach Geogria and Tbilisi in particular. Option for real romantics is to take a ferry from Odessa/Ilichevsk to Poti or Batumi, a bit long, but very nice journey. If you don't have time, then you can easily reach Georgia also with recently opened low-cost flights (Wizz Air, can be as low as 35-40 USD only) from Kiev, Kharkiv or Donetsk, all fly to cheap Kutaisi airport. Kutaisi to Tbilisi is easy and cheap either by train or bus
For Warsaw to Georgia (Warsaw to Kutaisi) you can as well use same low-cost company Wizz Air