Solartwin is an unusual direct system with flexible pipe and no antifreeze, and a PV-power pump. I reckon it's expensive for what you getb. In the UK I'd always choose an ET system rather than a flat-panel one, but in Portugal it may not make much difference. Not familiar with the Wolf kit, but a quick look on the net suggests they use fairly standard tubes. I can't find system details.

Ingleside. Yes the pump can be 10% if it's a big fat one on a small solar system, but that's just poor design. My pump is 12W, which is 0.7% of max system output (1.8kW), so a few % overall. And of course any system can have a PV pump if you like, but there can be issues with poor control due to there being enough sun to heat tubes but not run motor early/late in day. ET's don't leak anymore, so that criticism is just solartwin marketing guff. There used to be an issue with glass/metal interface on single-skin tubes but nearly all tubes are now double-walled with no glass/metal seal to fail.

Equally putting heat in the top of the cyclinder rather than the bottom is independent of panel type and can be done with inderect systems too. (again my system is like this).

So yes there are good features of the Solartwin system, but it's easy to use these with much more efficient ET panels _and_ spend less money. I do agree that these things are still not standard in ST systems. (The top/bottom issue and its effect on overall solar fraction is complex and depends on usage patterns and control systems, so which is best will depend)