Valencia vs. Tarragona for a home base (no car) ?

Why can't you start in Valencia and make your way to Barcelona via Tarragona?
Great restaurant in Tarragona - http://www.restaurantbarquet.com/wp/

That menu does look good, David, and I will probably make my way elsewhere along the coast,
but the pile of points I have to use up means I must decide between Valencia and Tarragona for 5 nights stay, hence my request for measured analyses comparing the two.

"Assuming that I will want to do a couple of day trips without a car, what are the pluses and minuses of each location? Highlights?"

Valencia is a big city and there is much more to explore than in Tarragona, especially when you're 'culture consumer'. In addition, you'll get better public transport connections for your day trips.

http://www.visitvalencia.com/en/home

Perhaps a better answer would be that both of these places are noted for attractions within the city rather than anywhere close by.

Tarragona has more options nearby for daytrips to spend 5 nights, but the city itself can easily be seen with only 1 night. I spent 1 night there and was ready to leave the next day. Barcelona is easily reached during the day but doing that for several days might get pricey and waste a lot of commuting time.

Valencia is a bigger, more cosmopolitan city that can consume several nights. But to me, 5 nights will be too much. I spent 2 nights there and would have enjoyed a 3rd, but more might have been too much.

Personally, I would pick Valencia and plan several day trips. Even Tarragona could be a long day trip if you get an early start. There are certainly plenty of dinner and evening options there compared to Tarragona.

Thanks for your replies -- I'm leaning towards Valencia, and thinking about whether to add Barcelona beforehand or afterwards, and other ways to round out the trip...

Just spent a week in Valencia, no side trips. The architecture in the Arts & Science & Oceanography area are spectacular, spent 2 afternoons there. The beach front is beautiful with 7km of boardwalk & transit system is good. Lots of bike paths for cyclists. The El Carmen neighborhood in the old town has great little restaurants and a jazz club Billy Glass. Restaurants enjoyed were Panorama terrace - great ocean views & food including paella, Seu Xerea, Refugio eu12 day menu, La Comisaria fusion & creative flavourful dimsum.

"I'm leaning towards Valencia, and thinking about whether to add Barcelona beforehand or afterwards."

This idea coincides with my original proposal. It makes sense.

I'm not sure if your question whether to add Barcelona at all or at which end to add it. Barcelona is a must-see! Add it. I'd go straight to Valencia (haven't been yet) as a place to relax a bit if you're arriving after a long flight (sleep-deprived, jetlagged) and then Barcelona afterward.

You may want to spend a night in Tarragona or you may want to day-trip from Barcelona.

How many nights in Barcelona? As many as you can manage. There's lots to see and do plus day trips. What time of year are you going?