Honestly, either. Budapest is much bigger but has excellent public transport. For Buda, I particularly like the thermal baths, the flippermuzeum (pinball), St Stephen's (used to be free, but noticed they now charge), the river and the fab views from it, fisherman's bastion is beautiful, Margaret Island (fountains, the parks and platinus pool) and the outdoor ruin pubs. Found the castle boring. Plenty of galleries, interesting museums etc. Riga is walkable in a day, and is pretty, probably not quite as much to do (it is nowhere near as big) although I liked the market, the KGB museum, and just wandering about, but my fave bit about Riga is it is very near the coast, when we were there we went to do the Kermeri Bog walk and also to Majori beach (which is beautiful with really nice houses nearby and a lovely street with restaurants on). You can get there easily and cheaply by train or bus. I think I would also consider the cities that suit your schedule best so that your trip is "comfortable / easy". What I mean is, when you move cities, you are probably checking out of a hotel / or accom, and this will be midday at latest, in a perfect world, you would then have a short flight, and you would land just in time to check in at the next place, no hassle. What is less attractive is to be checking out of one place at midday, and then not flying until 10pm, arriving in another country late etc. - I realise there is stuff you can do, stow your bags and return to hotel to pick up, use lockers, use uber or Bolt and so it isn't that bad, but it is just worth bearing in mind. All the cities you have mentioned are "OK" iro airport transport, public transport plentiful or ubers pretty reasonable. Vilnius is less touristy than all of the other places - still plenty to do, and if you like arty stuff it is quite a good city (Uzipis is a nice enough wander about). I have been a bit surprised how much these cities have increased in cost for eating out etc. in the past 5 years - Vilnius used to be very cheap, then Riga, with Buda next, then Prague, but now they all seem quite a bit more expensive and much more in line with each other - however, in general, it is still cheaper than the UK, and in the case of London as a comparator, quite a lot cheaper. I though Tallinn wasn't much cheaper than Helsinki when I last went, which is saying something ! PS, if you do go to Prague, the statues on Charle's Bridge are not the originals. To protect them, the real ones are underground in Vyšehrad Casemates - tunnels used to move soldiers about in Gorlice Hall - a huge cavern. I loved going here, unusual and historic. Hope this has helped and have a fab time - you can always go back another time and do another couple of cities x