In what way is Tyrian simpler? I'm something of a fan of both games, and I hadn't noticed Tyrian being especially simple.
Interesting thought. I think Tyrian does a better job of giving you choices than does Raptor. In Tyrian, you must choose between multiple secret levels, or even between the choice between a secret level you know you can reach and another of which you're uncertain; you must choose whether to go to an exceedingly dangerous level for the equipment which lays before or beyond.
In the shop itself, the choices become just fun.
Some weapons aren't worth the price you pay for them. Some are only worthwhile at higher levels, but may only be available now; in which case, do you sell all the levels of your other gun to buy it up, or do you rely on other forms of damage until that gun can be upgraded to usefulness? What if you are choosing between unique sidearms which have helped you up 'til now, or the new and strange sidearm which is in the shop at hand, costs more, but is very affordable?
As a further note, the variety of different sidearms and the power plant mechanic allows you to have distinctly different playstyles as well - you can go for powerful weapons you can only occasionally use, or balance for constant output; you can pick a ship for its stats or for a special ability you can really use (armor regen!!), and you can choose different weapons depending on how you like to fly and fight -- e.g. the flamethrowers are very powerful, but only if you are willing to get up close and personal and fly very aggressively, and depending on your weapon layout (and the level you're in!) you may get more value out of the uber-weapon powerup or out of something more defensive (or possibly something else - the fireblast one in particular has some unique uses as well).
I think Satertek may may just have been referring to the ease of playing - Raptor is much less forgiving, and with fewer options (particularly early on), you can't really change your approach to a level that's kicking your behind, you just have to try over and over until you get it right. Tyrian's richness of options make it easier to change your loadout or even fly the level differently (avoiding some reward sections, for example) - you can see simple solutions, while in Raptor it's not always clear what you're doing wrong, you just keep running out of health before the end of the level.