IMO, if you're only going to be a certain level for just one session of play, it's pointless to even have that level. Beginners don't even have time to get used to their abilities and then you're making them level their character right away. I think a lot of beginners would be tired of working on their character at that point, having just made it earlier, and then bam, at the end of that same session, they're supposed to level up? It totally defeats the purpose of giving them time to familiarize themselves with the abilities they already have and will probably give a lot of new players the impression that the game involves a lot more bookkeeping and character building than it actually does.
Personally I like trying out as many characters as possible (unlike others who want to always play a Wizard or a Ranger for instance), and I already know that I will want to start at level 1 each of them, so if there's 10 classes, that could be 10 evenings of play.
Then, one of my old pet peeves in RPGing is seeing characters level up before the players had time to try out even half of the stuff they got at the previous level. I just hate to see players accumulate stuff and more stuff every level, and never use half of it. This is IMHO a symptom of the game giving on average more stuff than players can keep in mind and/or levelling up being too fast.
So for me starting with less stuff is good, because it forces the players to use that little stuff they have, instead of ignoring half of it, before they get more. But then I would also have to slow down advancement, as I have nearly always done and as other DMs have nearly always done when I played with them (can't speak about the masses, but slower advancement has been pretty much ultra-common in games I've been playing in, basically the only frequent house rule that didn't give
more to the players).
However advancement is really a piece of cake to adjust in every game! The books can suggest a certain rate, but every DM will do what they want really. And if I want to run a game that includes the years of apprenticehood of the PC, no way I'll have them level up once a session. IOW, I'm just not going to worry about the suggested level advancement rates.
The other problem I have is that you don't get a tradition, scheme, deity, etc. until 3rd level. To me, these are character-defining choices. I don't want to be just a plain wizard for 3 levels. If I want to play an illusionist or necromancer, I want to be one from the very beginning! I don't want to have to wait until level 3 before becoming different from others of the same class.
Don't know... They are indeed character-defining, but not all of them are suitable for
apprentices. I had several (casual) players in the past pointing out that in their opinion a Wizard choosing a "School Specialization" at level 1 made no sense. In my opinion it totally depends on the campaign... character A in fantasy world X can very much start at level 1 being a necromancer, while character B in fantasy world Y might make no sense that she can discover/understand such knowledge since day 1. It also depends on what benefits does the specialization give you, and how do you interpret them... 3ed specializations were so generic, that they could fit 1st level with no problem, while 5e traditions give the wizard a few tricks or boosts that might very much fit better a veteran.
That said, "Deity" is certainly something a Cleric should have chosen since day 1, but that doesn't necessarily imply that she should also get the
mechanical benefits of her choice immediately...