Hi Richie
Arrived back 2 weeks ago from Tuscany hiking in 30 C +, As someone who for years extolled the virtue of boots in all circumstances you can now rarely get me out of my Hoka speedgoat 5s, though they'd probably just about last the
Camino Frances but they'd be 'slicks' by the end.
What you'd wear in Ireland won't necessarily translate into what you'll need for Northern Spain, In the Uk I may well wear Salomon Quest 4 gtx in winter, they fit my feet perfectly, I would not take them to walk the Camino in June ( I speak from experience) also how far you're intending to walk in a day may well influence your choice, The above boots for me are limited to 10-15 miles, anything above that I wear trail runners for the extra forefoot cushioning. I can comfortably wear them at distances of 25-30 miles without suffering blisters or pain. For me the argument for boots only holds out if you have weak ankles, but the CF is almost entirely on good paths, roads or pavement so ankle support isn't the issue it would be in rougher terrain.
Now I weigh 15 stone, add a pack that and cushioning becomes even more important, my other half who weighs 9 stone and who from time to time walks with me is now also a convert to Hoka's which she wore for the first time and for the first time didn't get any blisters. ( I do not work for Hoka ;-) )
Another point for Trail runners is they adapt to your foot shape far easier than boots do.
Gore-tex, In June in Spain? for me ? Certainly not! Let your feet breathe!
My pilgrimage footwear experience is...
Salomon 4 gtx: Good boot, Good grip, good ankle support, Durable sole, way too hot for Late spring and summer in Spain. Limited by forefoot cushioning for longer days.
Salomon X ultra mid: Very light, poor grip in the wet, wear very quickly for a boot, forefoot cushioning poor, again limited on longer days.
Lowa z-6: Didn't feel that good once under way, poor grip, poor forefoot cushioning. Didn't wear them for long.
Altra Olympus trail shoes: Very comfortable, roomy, excellent cushioning, excellent grip, durable sole. Only recommended if you can cope with the zero drop. I found that they strained by tendon a little but no so much as to stop me.
Hoka Stinson 6: Very comfortable, excellent cushioning, will cope with long days, questionable grip on some surfaces, uppers wear quite quickly may not survive the trip!
Hoka speedgoat 5 gtx : Very comfortable, excellent cushioning, will cope with long days, very good grip though not quite as good as the Altras. Uppers hold up very well, in fact better than the Salomon boots over 500 + miles. Sole wears quickly but even when smooth still retained good grip on most surfaces. A little warm in hot weather.
Hoka speedgoat 5: Non gtx. review the same as the gtx version but with the bonus of being cooler which is ideal for warmer climates.
if you were venturing into rugged terrain I would always recommend boots, but the Camino is not 'rugged terrain' so I'm comfortable with recommending trail runners.
I hope this helps but as with all footwear you'll never really know till you're on the walk.
Martin