Always just outside, unless you must always be in the city centre. Glasgow hotels are often very expensive, but you can just as easily hire holiday cottages near Glasgow – like https://www.finlaystonecottages.co.uk/ – for a fair price. These cottages are often within a 10-30 minute journey into Glasgow via transport, offering a quieter and more comforting experience.
Many times, staying in a hotel in Glasgow itself means that you are often dealing with a lot of noise out on the street. Even the best hotels can struggle to keep the noise pollution down. You also will find that you pay a hefty premium for the chance to stay in the city centre, and it can become very expensive.
I would always advise getting a hotel – or cottage – just outside the city. It is cheaper, easier, and generally better value for money.