I personally find that grid based system actually entail greater strategy than free form maps.
I don't agree. I think the strategy required is just very different. And I think grid-based combat tends to be even more predictable than free-map combat. Take HoMM, for example, or King's Bounty. After playing any of those games for a couple weeks, I can predict exactly where each enemy unit will move and what it will do - with an accuracy rate of 95% or even higher. And when you know what's going to happen to such an extent, it's pretty easy to figure out what you should do. And it provides you with a huge advantage over the AI, which generally has no clue what your next moves are going to be.
People often complain about how easy it is to defeat equal or greater opponents in Total War games while taking minimal casualties yourself... But I actually think that's a greater problem in games like HoMM and King's Bounty. To take HoMM specifically, I could utterly annihilate enemy armies three times the size of mine with a superior hero and take almost no losses! And if you know what you're doing, you almost never have to adjust your strategy mid-match. For all but the handful of end-game battles, I could plan out at the first round exactly where every troop on the field (mine and the enemies) would go and what it would do - and pretty much the only times I made a mistake was due to the RNG producing extreme values.
Compare this to games with free-field combat like Total War, or even RTSs (even though the latter, at least, isn't a perfect analogy). I could often predict the overall flow of battles in these games, but never to the same precision as in grid-based combat. The result is that I have to deal with the unexpected much more often, and I have to reevaluate my strategy on some level, even if it's just in the details. Maybe I didn't expect those charging troops to break through my defensive line and didn't prepare adequately for it, for example. Or maybe the terrain is such that my normal strategy isn't quite applicable or results in something playing out differently than I expected.
Sure, there is strategy involved in mapping out the exact course of a battle, and in particular determining how to influence it in a way to minimize your losses. But there is just as much strategy in free-field combat where you can't always determine exactly what's going to happen or how it's going to happen - you have to adjust for the unforeseen or unexpected more often, and that is simply another kind of strategy. Personally, I enjoy both kinds. However, Brad Wardell has gotten it into my head that we'll have combat like the Battle of Five Armies in the Hobbit, and the Battle of Dagorland at the end of the 2nd Age in Middle-Earth. Watching such battles play out in a free-field combat system would be far more engaging and aesthetically pleasing than in a grid-based system. The biggest reason for this is probably that in free-field combat, everything is happening all at once - it feels real, while in grid-based combat the armies just stand there staring at each other most of the time...