I have similar route, Belgrade to Odessa; wondering if the way (which make sense in terms of time/money) Belgrade to Odessa will be via Chop as well. Or there is better options via Romania?
Let's just compare:
a) direct train #108 Odesa-Chop (19:02-13:31, 'kupe' ticket for 28/03 date is 170 UAH), then Chop to Zahony (14:08-13:26) and Zahony to Budapest (14:03-19:32 or faster InterCity train (will require compulsory seat reservation) 14:30-18:37, one through ticket Chop-Zahony-Budapest is 18,4 euro. And finally Budapest to Belgrade (22:20-6:32), ticket is 15 euro (+ possible sleeper reservation). In total all adds up to roughly 50 euro and 37 hours travel time (nigh-day-night)
b) don't know about any direct buses from Odesa to Bucharest (and doubt there are any), so let's consider complicated way with changes - Odesa-Reni-Galati-Bucharest. Odesa-Reni is 5:30-6 hours and 120 UAH by bus, let's say you will manage to make those 20 km from Reni to Galati (via Moldova) by hitchhiking for 2 hours at best, then Galati to Bucharest either by direct bus (4 hours & 45 RON) or direct train (one through ticket Galati-Bucharest-Timisoara for 135 RON), timing with train can be 17:40 dep. from Galati, arr. to Bucharest 21:25, dep. Bucharest by
mentioned in other topic train to Timisoara at 21:46. Schedules for the rest of the journey you already know from the same topic, ticket fare for leg Timisoara-Vršac will be roughly 5 euro, Vršac-Belgrade is 320 RSD). So in total let's say it will be day-night-half of the day (as you see a bit faster than via Chop-Budapest) and pretty much same 50 euro for tickets, however more complicated in terms of number of changes, hitchhiking over the border etc.
c) it is also possible to manage Odesa to Bucharest leg in more convenient way - first by bus/train to Chisinau and then by bus/train to Bucharest. However such route will be longer and more expensive. Also with this option it is possible to substitute Bucharest with Iasi and try to go directly to Timisoara from Chisinau, although it's not that easy to do by train, since overnight trains Iasi-Timisoara arrive late for change to Timisoara-Vršac train (unless you want to be in Belgrade in the evening). And we not sure you would want to travel all the way from Chisinau to Timisoara to bus just in order to catch morning Timisoara-Vršac train