Materia never had a noticeable impact on characters. Even altering their HP and MP, or other stats by what should be noticeable percentages does nothing to really affect their effectiveness in battle. Some are good at physical attacks, some aren't, and everyone can rock the house with magic. There was no strategy in FFVII except attack with magic (particularly if the enemy is weak against something), heal when you need to, and use limit breaks as soon as they fill up. Even if you're a little underleveled, that will pretty much guarentee that you never die. I'm not going to sit here and claim that a game like FFVI needed more strategy than that (despite being my favourite it really didn't though boosting stats makes more of a difference in it), but I've played VII more than enough to know that it's stats, weapon differences, and characters don't really matter. It stands as one of the easiest games in the series.