Oh god, only 5? Well, off the top of my head.
Hypershade vs. Rendertree w/Compounds. This one is a no brainer, they Hypershade is the same limited interface from early Maya releases. While Soft’s Rendertree has input ports listed on each node, that are collapsible if you don’t want to see them, Maya tucks all that into a very inconvenient/convoluted connection editor pop-up that doesn’t even show data types for outputs and inputs. Completely missing compounds, etc. etc., the Hypershade is dated and simply bad. Little things, like pulling down a menu, and shift clicking display flags without having to constantly dive back into the menu or tear it off. Little things, like one hotkey for parenting that depending on which mouse button you use, determines whether you set your selection as a child or the parent. Sticky keys. (aka like in photoshop when you alt-click to sample a color while painting, once you let go of alt, your are back to the paint brush without having to press ‘b’ again. Sensible, brilliantly thought out defaults for hotkeys and menu/interface. I’d add to this to get rid of the stupid messy shelf system and spacebar menu altogether (or at least make sure the interface is great with the shelves hidden). The big problem with Maya and Max is always that each seat is customized. I can’t work fluently off a default Maya install and if I sit at your desk your customizations aren’t going to be the same as mine, I always have to start by loading extra tools, making custom shelves, setting custom hotkeys, etc. etc.. I don’t even want to have to load a custom user file. With softimage, I can sit at any machine, make sure it’s set to the system defaults which it usually is, and every tool is where it should be with great hotkeys. These ones are important to me but there are so many more. It’s a shame that Autodesk, sometime over he last 6+ years, didn’t tackle Humanize Maya first before EOL’ing Softimage, if they are serious about this now however, they have a lot of hard work ahead of themselves. I’m hopeful but sadly not confident, though I do know they have good devs over at AD, hopefully they will get the go ahead to work their magic, if so they might just pull this and more off.