From a pure regen standpoint, +5% mana is actually better than +3% spirit (or the flat +300 spirit you get from being a panda.)
Mana tea is effectively +3000 mana per chi spent, so a percentage increase in mana pool grants an additional x% of 3000 mana per chi spent- so 5% mana gives you an additional 150 mana per chi spent.
At 10k spirit, on the other hand, +3% spirit is +300 spirit (ie the same you get with the panda food buff,) or 168 mp5 in combat. This means that you only have to spend 1.12 chi every 5 seconds for gnome regen to beat human or panda regen.
Human will obviously get better as you gear up and panda will obviously be better in situations where you want more throughput rather than more spirit, but at lower gear levels the gnome racial wins out for regen.
And on the subject of racials- for my Horde bros, Arcane Torrent is 1 chi every two minutes, effectively being 3000 mana every 2 minutes, or 125 mp5. Inferior to the panda racial in regen, but the bonus chi is also effectively a throughput boost.
Also note that the int/+2% mana meta(Ember) is not better regen than the spi/crit effect meta(Revitalizing,) since it's only +60 mana/chi spent vs. 243 mp5, so you'd need to spend 4 chi every 5 seconds to break even.
EDIT: Oh, right, you also have to factor in the max mana boost in the mp5 as well- 5% is 15000, 2% is 6000, so that makes it 50/20 mp5 in a 5-minute fight or 25/10 mp5 in a 10-minute fight. Doesn't tip the scales towards the 2% meta enough, but it does increase the amount of spirit you need for the human racial to overcome the gnome one.