Thanks Mark. You are absolutely correct.
I try and check things before I post because things do change. So I went to RegioJet and typed in Budapest to Vienna and all the trains were shown to originate at Budapest-Kelenföld. I knew the trains used to originate at Budapest-Déli pályaudvar (literally Southern train station). So after your comment I changed my search on their website to Budapest Déli and sure enough they do still originate at Déli. I wonder why when you do the city search they don’t send you to the station of origination. Strange.
Anyway. Déli is almost exactly 30 minutes from the Oktogon on Andrassy ut using the M1 and M2 metro lines. Kelenföld is almost exactly 30 minutes from the Oktogon on Andrassy ut using the 4/6 Tram and the new M4 Metro Line. So that’s a draw. Taking the train from Déli adds almost 15 minutes on to the trip to Vienna (2:47) as compared to starting in Kelenföld (2:34).
Neither Déli nor Kelenföld are anything to be excited to see. Both commie era creations. Both mostly outside plazas with very little “station”. Kelenföld has some newer renovations as a result of getting connected to the new M4 metro line some years back. Déli https://youtu.be/4gw7fkp2XsQ?si=dg75ddbfAWCiNo4L Kelenföld https://youtu.be/ylzKCYyQYwU?si=36u93XnmKPFe806T
If you go back and look at my post, I also said, “but I'll stick with MAV/OBB for the Keleti Station convenience and experience”. Yes, convenience is marginal. You can get from the Oktogon to Keleti pályaudvar (literally meaning Eastern train station) using the 4/6 Tram and the M2 Metro in about 10 minutes or there is a bus that is a few minutes faster. You could even walk it in 30 minutes.
But the experience. This is a personal thing. I love great old train stations, and I am on holiday so that influences decisions a lot. Keleti pályaudvar is a great old station. https://youtu.be/ylzKCYyQYwU?si=36u93XnmKPFe806T The guy in Seat 61 says “Budapest Keleti is one of Europe's great stations, with graceful architecture and trains arriving & departing to or from ….”
Travel time from Keleti to Vienna is 2:38 on the high speed RJX train or 2:40 on the EC Trains (LOL!!!). So about half way between the time from Déli or Kelenföld.
But the RegioJet trains do have a lot of creature comforts that the national trains do not have. Its why I love private enterprise over nationalized services. On a long haul, like Budapest to Prague, I would think really hard to give up those creature comforts just to leave out of Nyugati pályaudvar (literally Western train station) ………….. but the Eiffel constructed station is also one of Europe’s great stations. https://youtu.be/d2AdH-BmKJM?si=FK56cFgTb0TxDi67
Mark, I always appreciate corrections. How I learn.