I'm wondering if anyone uses a synthetic blend oil because they feel it is better for their engine than (a) lower priced full synthetics, or even (b) any full synthetic available.

Full synth all the way. Its been engineered to maintain peak oil properties far better than a blended or mineral oil ever could.

guess the question your asking is a synthetic blend MOTUL better or worse then say a syntheic brand valvolene? i guess it would have to do with the standards but i would say a full synthetic regardless of brand will do a better job as described by the standard then a syntheitc blend would, but would this tranlate into better for your engine? i dont know.

I use Castrol EDGE 5-30w full syn, mainly due the high revving nature of my engine. its a great oil. penrite is a staple on here and although i havent used it , by all accounts it is excellent. a good synthetic is superior in many areas, more resistant to break down and foaming of the oil , cleans the engine more effectively hence it often blackens quicker in first time user engines, but holds these deposits in suspension and prevents wear more effectively. an oil that stays clean over 5000 to 10,000 kms is not doing a good job of keeping the engine clean. to me paying extra for decent oil is a great investment. so many people upgrade cams etc and skimp on oil!!

No-one has put the case that semi is better than full synthetic.
Looks like people use "semi" synthetic either because the budget is tight or they just don't like spending the extra.
I wonder if they realise that their "semi" is probably only 20 - 30% synthetic.

Must admit that I used synthetic blend last 2 changes (previously straight mineral oil).
I intend to go full synthetic next time if no-one gives me a good reason not to.

My logic for using full synthetic is best for the extended service interval of 15000kms. It may cost almost double but when you do the maths, the labour, oil filter, oil disposal costs will make up the difference when serviced say at 7500km with semi synth. Most Full Synthetics also reduce engine friction hence reducing petrol consumption a little more.