PH - Only played this and ST once, gonna revisit soon, but I don't think the replay value is that much
ST - See above
Since this post I have re-beat PH, and am currently replaying ST.
The controls in both games, I'm sorry to say, are horrific. I remember back in the day having problems with them, but after revisiting them, they have not gotten better.
It's a real shame because I really, really like a lot of things about PH. I even moved it up on my list, higher than several Zelda games which are technically not as flawed. But for the stuff I like on PH, I really like, which makes it higher on my list than some others. But the flaws are horrible and really shouldn't be there. The touch screen is really bad. Not sure if its my 3DS, but some of the touchscreen stuff functioned fine, such as selecting and using weapons. It was the drawing stuff on the map and slates which was utter failure. I could do a perfectly good drawing and the slate would not recognise it. Then I would do the EXACT same thing, and the slate recognises it fine??? Same thing, same starting positions, everything. Furthermore, some other slates accepted no matter how crap the drawing was. I could do a pathetic drawing of the first slate on purpose, and it accepts right away. For the second slate however, I would do a perfectly fine drawing, and it would take about 5 attempts for it to be accepted. Drawing on the map never registered where I pressed - it always did it a couple of centimetres to the left or right, which made it a nightmare. Rolling was bad too. The pirate lady repetitively ambushing you, ruining exploration. The fishing giving you the same fish over and over until you try for absolutely ages as its random. And of course, the temple of the ocean king. And the stylus controls in general were very tiring for me, I prefer buttons any day. These things bring the replay value of PH down. On the plus side though, I love salvaging, the ocean in general, I actually like the transport method (the automation worked for me as it was a break from the tiring stylus controls), and of course Linebeck is awesome. The last boss is great and epic, and the ending is very cool, especially the linebeck ship part at the very end.
ST, unfortunately, has the same control problems as PH for me. In fact, probably even worse. Selecting the route is a major problem as it doesn't register well. (Selecting it was never a problem in PH, the drawing was, but selecting the ship was fine). Rolling seemed better at first, but because it's 2 taps, it interferes with combat. Furthermore, the travel system is way worse, and the dark trains ruin everything. And to top this all off, I'm just not as interested in ST as I am PH in general. At least with PH I could like it through it's flaws because of the things I liked. But ST... seems just ok but not superly interested, and so with so many flaws, I think this game is gonna suffer in my rankings.
So yeah, replay value - as much as I like PH, replay value is low. And ST replay value I think will be even lower.
Regarding touch screen issues for both games, as I said I am not sure if it is my 3DS, but some things are fine while others not. For PH, not registering where I pressed was only an issue when drawing on maps. Actually playing the game as Link, selecting and controlling weapons such as the boomerang, and attacking enemies, were all fine.
ST the same, just maps. I've now re-calibrated my touch screen, and no different - but I read that does nothing anyway...