Launching one year earlier helped Microsoft, having a cheaper console, having third party games not skip the platform, having the best version of games for a majority of the generation all went hand in hand with their investment in first and second party.Huh? Your examples undermine the point you're trying to make.
The Xbox sold less than 25% of its direct competitor while being significantly more powerful - but also launchong much later.
The 360 only managed to match the PS3's sales while essentially being roughly the same in realworld performance (PS3 on paper had more shading performance - so going by the flops numbers people are so obsessed with PS3 was more powerful), despite launching a year earlier and Sony's monumental fuck-up with the PS3.
The 360s successes had more to do with its ability to match PS3 on library, together with MS's first party juggernauts over the first half of the gen.
So the above examples aren't in any universe examples of more power helping sales success. You can't even justify from that an argument that power advantage made any difference at all.
One could argue that Microsoft would have done much better if not for RRoD and the amount of money they had to put in for extended warranties.