Both Blazing Sword and Sacred Stones are really good, and you can't go wrong with either. Sacred Stones is the more polished game (doesn't have a weird issue with going several chapters without shops) and is the better-written one, but FE7 has much more varied map design (and the ranking system makes a good in-game challenge). Also FE8's normal mode difficulty is broken and promoted enemies are way too weak. When I was younger I disliked the fact that FE8 let you grind between fights but now I no longer care, since you can always choose whether to do it or not.
Binding Blade is generally worse than both unless you're seeking a challenge.
going several chapters without shops is a benefit to FE7. ---