If the physical specs are any indication load times aren't something we'll have to worry about on either platform. There's also no reason to believe Sony is going to be any more developer friendly than Microsoft. If anything, based on the actual history of both companies MS will be the easier console to develop for. That being said, odds are they will both be on a similar level with a slight nod going to MS for developers working on multi-platform games.
Possibly. I'm not a console developer, but keeping an ear toward the industry, it seems whichever console brand is running in 2nd place is the one that publishers have an easier time getting along with.
Case in point, when the 360 was going strong against the PS3 - Sony was all about cross-platform and online play: you didn't require a PS+ Sub to play online, they were open to cross platform, and it was Microsoft that ~required~ XBL Gold from the player and wouldn't allow cross-platform. One generation later, near total reversal.
Devs, well, that's moreso set by engineering at the hardware/API level. But Devs and Pubs go hand in hand, so I guess it doesn't fall far from the tree.
I do suspect xGryfter is correct - Microsoft will probably be more willing to play with third party Publishers: they don't have a strong first party hand to play upon release (I think they would be better served waiting for release until they do, but I'm armchair QB'ing that one), and they have to rely on third parties bringing strong titles to XBwtfeverwearecallingit~1, and they will be much more accommodating with respect to licensing, access, and royalties. Bridging the Xbox with Windows (XBGP for PC, DX12 Ultimate, etc) will go a long way for Microsoft - it could even make the hardware platform irrelevent if MS wanted to let it evolve that way (again, armchair QB'ing it, I think they would be better served getting out of console hardware and leaning on PC and Cloud).
But I also suspect Sony will have the numbers, and Publishers will want to be there - Sony hopefully won't play dumb and wall their garden completely off, or be unreasonable with fees and access (they have relented a good deal on the PS4 with respect to cross-platform play, so that's a good sign). So long as Sony doesn't try to strangle every last dime out of the Pubs, they will remain eager to get on the platform even if it does cost them a bit more than it does to get on Microsoft.
