I can give insight on the sliding ladder. Before I sold my RTT, I wanted a telescopic. The sliding ladder worked great with a few exceptions.
1. Not enough settings. I drilled extra holes to give a better range.
2. The rungs became loose over time. Not enough to be an issue, I just wasn't happy with it. By design, the one I owned, there was no way to tighten the rungs without breaking the covers over the screws.
I looked into swapping to a telescopic design. It really wasn't going to be that difficult if you can make your own mount. I studied and measured quite a few ladders. I just never got around to swapping them. I did notice there were two different designs of telescoping ladders though. One slid to where you want and twist locked, the other was just a round tube version of mine, with buttons you depressed to change to a fixed height.