When we planned our 20 night trip, most (Reddit and RS.com) recommended that we limit our Bratislava visit to just a day trip from Vienna.
I am glad we stayed at least one night in this underappreciated city. The Bratislava Castle is certainly does not compare to Schonnbrunn in Vienna, but the ticket is only €7 and that also gives you admission to all the other museums in Bratislava. The food and drink is about 30% less compared to Vienna. Lots of people just eating, drinking and having a good time. The locals were so friendly.
We stayed at the VIP Apartments by St. Michael's Gate in the Old Town. We saved about $40 per night over another hotel night stay in Vienna.
https://maps.app.goo.gl/4mjNWsMvFKFguXPe9
I would have liked to have stayed longer.