Wands vs Sceptres?

Disclaimer: I am new and am trying to learn more about the game.

I'm following Enki's Arc Witch guide and am trying to understand a few things. For this build, Enki says that you could use a wand or a Sceptre (or a Rune Dagger but I don't care for those) and lists 2 choices. The wand being "Onslaught Call" and the Sceptre being "Demon Call". My questions are as follows:

1) Are the choices listed for "endgame" only? And what one should strive to get?

2) In general, I would like to use a Sceptre vs a Wand for the looks and MTX options but from what I can tell, a Wand will be stronger than a Sceptre in terms of spell damage and such. Am I wrong in thinking this? Why would I choose a Sceptre over a Wand (if we take out the looks etc)?

Link to build guide: https://www.pathofexile.com/forum/view-thread/1147951

I can't answer for the 1, but I can for the 2

Wands increase Spell Damage, whereupon Sceptres increase Elemental Damage. Maraketh Wands increase cast speed, whereupon Maraketh Scepter will penetrate elemental resistances. There are also a special kind of Wands that have no implicit bonus and, instead, allow for Minion mods to be rolled on them.

A regular wand should be slightly better than a regular Sceptre when it comes to elemental spells, and will be definitively a better choice when it comes to physical and chaos spell. The only exception with elemental spells are Fire spells: Wands would only boost the spell's Hit, whereupon a Sceptre would also boost any Ignition that spell may cause. Usually, elemental spells with a DoT component (Vortex, Arctic Breath which has been recently renamed) also have a "Increase and Reduction to spell damage also applies to this skill's damage over time", which will make Wands boost all of those aspects.
Maraketh Sceptres can turn better than wands when going elemental if you focus a lot on damage penetration. If you manage to penetrate an elemental or chaos resistance to the point it gets negative (Remember when you ended Act5 and Act10 and all your resistances went negative?), that will be "considered" as an Increased [elemental] Damage Taken. They will, however, lose any vantage when it comes to DoT spells, since DoTs (like Ignite and Vortex's DoT) cannot penetrate a resistance.

An addicional, notable difference, may be in a Sceptre's ability to use Leap Slam for movement, rather than just a Dash/Flame Dash/Lightning Warp. This comes useful to a mage Inquisitor in order to get the full bonuses that his Instrument of Virtues provide them.

This only covers the main difference when it comes to spellcasting. As weapons, the two items are totally different and requires further explanations and con-pro evaluation

EDITED: Just realized he/she is a caster so Spellslinger is not that useful

Right, totally forgot about Spellslinger. Also, being a caster does not make Spellslinger useless. On the contrary: Spellslinger can apply both on Wand attacker in order to easily proc curses or other debuff before hitting, or as a boost on spellcaster in order to cast 2-5 spells with a single "attack"

Spellslinger is also something exclusive of Wands, and will allow you to cast one or more spells when attacking. It will also give the base damage of the wand as added spell damage on those spells you are supporting with Spellslinger - since most wands deal Physical Damage, it gets very useful for a physical spellcaster (Wave of Conviction, Bladefall, Bladeblast...). The trade-off is mana reserving and a natural cooldown of 0.5 seconds. In other words, you cannot cast, or better, trigger Spellslinger-supported abilities more than twice per second

Since you go Arc, however, you might want to use Brands or Traps if you don't want to self-cast them yourself, rather than bind it to wand attacks