@crbonade, good luck with your choices, I'm sure you will enjoy whichever variation of the CP you choose.
I just finished my first Camino last week (the Primitivo), and a pilgrim I met along the way recommended the Portuguese (from Porto) for my next one, since I can't get a lot of time off work at once. He specifically recommended the Coastal, since it can be done in a relatively short time (I did the Primitivo in 12 days, as a point of reference).
Firstly, the coastal is not shorter than the central. Actually I believe it's a bit longer if you take the coast as far as you can.
Edit: either way, it’s shorter than the Primitivo.
I'm starting with that as a planning point, but out of curiosity, what is everyone's favorite 'variant'? I'm contemplating Coastal/Litoral combined with the Spiritual, probably for a May Camino in the next couple of years.
Many people opt to start out on the coastal because the first day or two on the central are not as nice. I liked staying at Mosteiro de Vairão on the first night on the central (and met camino ninja there, RIP), but it's true that there are some busy roads getting out of Porto and a lot of cobblestones later on.
If you start on the coast, there are (I believe) three main options for getting back to the central, which you will have to do eventually.
1) Leaving the coastal at Vila do Conde, giving just 1.5 days on the coast but allowing you to return to the central in time for Barcelos,
Casa da Fernanda and Ponte de Lima, meaning that you basically don't miss any of the highlight places of the central. If you want to largely do the CP central but with a nicer beginning, this is the option for you.
2) Leaving the coastal at Caminha, meaning you spend longer on the coast and get to experience all the Portuguese part of it (e.g. including Viana do Castelo), and heading inland at the Minho river, joining the central at Valença but missing the places listed above. This option gives the most even split between the two.
3) Continuing all the way on the coast, including Oia and Baiona, via Vigo and joining the central at Redondela, missing Valença and Tui on the central. This is if you really prefer the coast.
Basically, it depends on how much you want to be near the ocean. The longer you stay on the coast, the more interesting cultural/historical stuff you'll miss inland. Personally I prefer the cultural/historical stuff, and I didn't find the coastal scenery to be outstanding, but of course there are others who prefer the coast. Up to you.
Regarding variants on the coastal, on the typical days three (from Esposende) and four (from Viana do Castelo), the official coastal route heads inland but you can choose to stay closer to the coast (the Senda Litoral). I took the inland route on day three and the coastal on day four and was happy with both choices.
Later on, in Spain, there is a coastal variant from Baiona to Vigo that was recommended and which I also took.
Finally, I highly recommend the Variante Espiritual as others have. I've walked it twice and it's wonderful.
