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I just got a lvl 20 Rotom (I caught it in the chateau), and I have a lvl 21 Luxor, which will eventually arrive through Luxray. Should I keep my luxor, or switch it out and take Rotom into my team? (I just got platinum three days ago)

That's what I figured. Plus, it'd be protected from normal attacks.

BTW if you have platinum you'd find Rotom in the Mansion. Just go through the enterna forest to the old mansion, go up to the second floor, and go through the center door. in the hallway, go into the second room. Go look at the tv. ^^ It's hiding in there.

<< I used Luxor to kick it's a**. Since it seemed to be obsessed with thundershock, and luxor can spark it without knocking it out. ^^

so I think I'm gonna use both.

If you battle competitively, an EV stat trained Luxray beats out Rotom, partly because it is often banned along with other legendaries.

a.) Rotom is not legendary. Its alternate forms which are event only are in the standard tier, but its base form is in the Under Used tier.

b.) Luxray isn't even that lucky, and is a member of the Never Used tier. A Choice Scarf set may be useable on a Luxray, but its move pool leaves a bit to be desired.

Between the two, I'd say Rotom is the better choice due to the fact that it's much more versatile. It sports two weaknesses, five resistances, and three immunities (one of which would normally be a weakness) to Luxray's one weakness and three resistances. And that's without the benefit of the five alternate forms (which statistically are actually superior to Luxray in overall spread). Naturally, it also gains the benefit of a second STAB, and also has access to better status inducing/disruption type moves, which allows it to function as a special sweeper OR a supporter.