Well, I was once a Pentecostal myself, in fact that was my first experience as a christian. My grandmother was Assembly of God before being AoG was cool.

From way back in the '30's.
The reason I progressed from Pentecostal, then to Nazarene, which is non-charismatic arminian, to finally calvinist, then Presbyterian was this: I found that the teaching and practice in Pentecostalism was consistently inconsistent with scripture. The way the charismatic gifts were practiced never jibed with the Word. Tongues were rarely interpreted, women were speaking in tongues and giving prophecies in Church, which seemed pretty strange that the Holy Spirit would be behind something He had expressly forbidden in His Word - women speaking in Church, etc., etc. Then in the Nazarene Church I found the twisted way they tried to explain away God's sovereignty in man's salvation to make man's ability to decide one way or the other the deciding factor was completely contrary to scripture. A Sunday School class on the book of Ephesians was the clincher. Over and over I heard, "It may sound like this, but what He really means is that.", to the point that it was incredulous.
Prior to that I had begun a more in depth study of the scriptures and Church history. One night I read the book of Romans all the way through, and the next day went to get a haircut at a barber shop I'd never been to. The barber happened to be a Reformed Baptist pastor. He blew me away as he began asking me if I were a christian, then if I understood the implications of the fact that all of existence was about God and that man was just one component of a creation made for the purpose of glorifying that God. As he expounded on the doctrines of election and God's sovereignty, Romans for the first time made cohesive sense. He was a Greek scholar, had in fact translated the NT into english for himself, and I left there with an armful of tracts by Pink, Spurgeon, Luther, and a book by Sproul. I was flabbergasted, and I was afraid. If what he was saying was true, then all that I had been told was false, and the fact that I had already begun to question why what I had been told never seemed to agree with scripture made me even more afraid. I feared I had never really heard the Gospel, but instead had been hearing what pleased my itching ears. I ran from calvinism as hard as I could. I read Finney. I read Compolo. I even went back to a Pentecostal Church. Nothing helped.... it all contradicted God's Word.
They all made it out as though God owed me a 'chance', and that He would be unfair to have either chosen me or rejected me before I was even born and could make some freee decision. But I knew my heart... it is a wicked and unfaithful thing. I also knew that God knows all things, even the end from the beginning, and that He has power over
everything. The only way I could ever have 'decided' for anything good was if He'd made me willing and able to do so. I could have no confidence in my own 'choice', so if there is any 'choice' involved, it had to have been His. And the only thing that could differentiate me from my godless neighbor is that He'd 'chosen' to MAKE me know and love Him, and hadn't 'chosen' to do that to my neighbor. It couldn't be that I was wiser or 'better' than that neighbor, because I wasn't.
So I began to study the scriptures more in depth, and what various Churches taught. Read more of Church history. And I was finally amazed to find that the old Presbyterians had been more close to the scriptures than any other I could find. You can imagine my shock, since my Dad, who was a profligate unbeliever, was an elder in a Presbyterian Church of the PCUSA. I had called them 'flatlanders' and apostates. And they were. Then I learned that there were a few small Presbyterian denominations that had departed out from that one long before because of its abandonment of the truth. But I was still not convinced.
So I sat down and came up with a list of ten questions that were very basic to the teachings of scripture, and started calling Churches of every stripe. Baptists, Nazarenes, AoG's, Pentecostal Holiness, Churches of Christ, Independent Bible Churches, Episcopalians, and Presbyterians. Every protestant Church I could find. From the most uptight to the most social to the wildest charismatics. And most couldn't even get past number four, some got as high as seven, but the only one in my area that got all ten questions right was an old PCA pastor, and that's where I finally settled. Ain't perfect, but it is closer to what scripture teaches than any other around here, so I'm stickin' with it. Been in that denomination almost 12 years
So for this presby, the main question I would have for a Pentecostal is, why do you listen to the hooey you're being spoonfed that appeals to your pride and flesh, instead of what the Word of the Living God says?