I was a FFXI PS2 noob and then turned PC after my PS2 started to lag and my wife said "stop taking the TV from me!"
So... We can't compare the NEW FFXIV because of the NDA. However, compared to the 1.0 FFXIV, we can go all day. I played FFXI on and off after 2010 but I did get Abysea and the 99 level caps, new age stuff, so I know how that games has been going. I joined FFXIV in April of 2012 and have enjoyed it very much. I would say the biggest draw for me and probably a lot of new comers will be the increase in the ability to casual play. I have a Wife, two kids, and a job (sorta), so I can't play FFXIV as I used to play FFXI., I was 19 when that game came out for me and I'm 28 now. That being said I feel like the 20min here, 1hour there, 2-4hour over there, gaming sessions are fun, enjoyable, and in the end entertaining enough to make me want to come back. I was even able to jump on for 20min, and feel productive. Where in FFXI you had to plan on staying an hour and then to feel satisfied another hour just to get some decent EXP or do some type of an event. Then there are Sky/Dyna/Sea Shells (haha) where you needed 4hours or you were a crappy member.
In FFXIV you can solo level for a good deal of EXP, solo a mission, grab a few people to kill a monster, or skill up in a relatively short amount of time and if you have more time to spare, then you're gold. You can still static missions, GC, Primals, EXP, Craft, etc. for a long time and in most cases a short time. In my LS, I was able to jump on, do 2 Primal fights then leave. Its much more casual friendly and playing that way doesn't come with a huge gimp penalty. Where in FFXI you had to invest to get the sweet gear. Clearly the more time you play the more chances you will have to get better gear but you will still be able to get good gear without quitting your job. Ill say the Housing system is probably the time sink of the century though.
Overall, FFXI will never be replaced as my all time favorite MMORPG because it was my first and I played so much and created so many memories. Then there is FFXIV which for me is a great game and fits me perfectly. If you fit my profile you will love the game. Add in the hype of a better game than 1.0 and a successful transition and you have a sweet, new, Final Fantasy MMORPG.
I hope that helps.