For me, it's a no brainer. Get gooder, sorry, better, on piano. The only reason I would want to get to the level of a professional classical guitarist would be.........if I wanted to be a professional classical guitarist.
I guess it all depends on what you want to do, music~wise, with your life.
But it seems to me that you've already reached the decision you need to and personally, I agree with it.
As a side note, there are loads of well known instrumentalists that play more than one instrument. John Paul Jones of Led Zeppelin was a church organist who took up the bass because in his words, it was easier to cart about than an organ. As he got into sessions, his organist skills in arrangement came to the fore and he then got sessions doing arrangements for the Stones, Donovan and tons of others.
Long before he was recruited to play in Led Zeppelin, he was, on the sessions scene, one of the 'go to' guys if you wanted keyboards, bass guitar or arrangements done. He was making such a good living as a sessionist that people thought he was crazy to chuck it all in and take the risk of playing in a new band without a contract or record deal. He had also made so much money as a sessionist that it was he and Jimmy Page that financed the band in the early days {they had John Bonham on wages of £20 a week ! }. Oh and he could sing a bit too. He could've been a vocalist for Pink Floyd !
That's very cryptic.....
On the "Innervisions" Lp Stevie Wonder plays all manner of keyboards, all manner of synthesizers, drums and moog bass as well as singing lead and backing vocals. On a number of the songs, he's the only one playing.
Paul McCartney played bass, guitar, piano, organ, mellotron and drums on Beatle albums and other peoples' stuff.
Ronnie Wood and Jimmy Page were both bass players in the first bands they were well known in before becoming known as guitarists. Indeed, many of the first bass guitarists in popular music {Jack Bruce, James Jamerson, Carol Kay, the aforementioned Jones & McCartney, Geezer Butler, John Povey, John Entwistle, Roger Waters......} came to the bass from other instruments which perhaps explains the directions that the bass guitar went in. After all, it was almost an afterthought of an instrument originally. But that's another story for another time.
But it does lead to another related point to your OP ~ playing more than one instrument gives you versatility and scope in how you approach both other instruments and music in general. I started off as a bassist and when I started playing guitar, it gave me angles that I would never have come to otherwise. I used to say to people about my guitar playing that "I play guitar with a bass player's mind" rather than the other way around. I find that translates to mandolin, various percussion and VSTis too.
The list of multi instrumentalists could fill the available memory of some computers. That they may be jacks of all trades but masters of none is neither here nor there. It's like being a decathlete or heptathlete. You become known for your all round ability. Some people know and love Daley Thompson and Jessica Ennis but couldn't tell you which events comprise their olympic discipline !
