The app controlled give you a greater range of controls and, I guess, a closer interaction with the toy (when they work). As I said above, the experience using the app with an internal egg was terrible but they might work well with knicker vibes? I have no experience with this though.
In terms of remote control knicker vibes, my favourite two are not the priciest, which is excellent. They are the Mantric Knicker Vibe (currently 30% off in the black colour for some reason) and the Juno Knicker Vibe (currently out of stock unfortunately). The Mantric has great, deep, rumbly vibrations (for a small vibe) which is my clit’s preference. It’s a very effective knicker vibe. The Juno is my preference for night’s out with live music bands and lots going in because it has a noise activated mode which means it vibrates fiercely away when the surrounding noise is loud and when the bands are playing but the strength of vibrations reduces and is quieter when you’re in a quieter environment. The battery in this mode also lasts all night which can’t be said for many other wearable vibes. This music mode probably isn’t a feature you’d be especially after though as the thrill for you guys will be more about you being in control and it’s vibrations are not as rumbly as the Mantric so my recommendation would probably be the Mantric. Both these knicker vibes have remotes that work well from across a crowded room with no connection issues at all.
Very important though… these knicker vibes need close fitting knickers with correctly placed pockets!!! Close fitting for firm clit pressure and pockets for keeping placement on clit (…rather than them wandering off out of your knickers and down a trouser leg! 
). I have a number of sets of these that come with ready made pockets that I use with knicker vibes, unfortunately they have been discontinued for reasons I simply can’t fathom but I’m sure a needle and thread can do a good job with alternatives you and your Mrs might already have. I would not recommend the knicker vibes held in place magnetically, they are too heavy and weigh knickers down so there’s no clit contact!
Remote control egg wise, my top one is probably the Fifty Shades Relentless Egg, I wrote a review in 2014 and it still works perfectly and gets use almost a decade later which I think says a lot for it. There may well be better eggs now but I’ve not found them. As I said above, the vibes and weight are better with the Bloom but it’s app connection is so bad it makes it unusable as a couple’s toy out in public.
I would also recommend having a look at the eggs with attached clit vibrators on the arm. I can’t link the one I have as it’s not currently stocked by Lovehoney but it’s pretty similar looking to this Adrien Lastic one and gives the advantage of both internal and clit stimulation as long as the fit is good for the person wearing it.