In a Two-Headed Giant game, life gained by your teammate won't cause Excalibur II's first ability to trigger, even though it caused your team's life total to increase
(You change its toughness to activate loyalty abilities
I certainly have been having tons of success with blue, but the format is quite well balanced, so every color has multiple good decks you can get into
This ability is eminently impactful both offensively and defensively, as it can be activated before combat to make your creature unblockable by a specific color, or it can be activated in response to one of your creatures being targeted by a specifically colored spell to make it invulnerable
If youre worried about fakes, Alpha cards, foils, foreign cards, and older stuff are a better place to be than Modern or Standard right now
Modern mostly lacks both features