They are alike in that both happen on a table with oil, and that is where the similarity ends. They work towards different goals, with different techniques, for people in different places. This comparison helps you choose without anyone selling you anything.
A relaxing massage aims to release muscular tension and bring stress down: it is physical recovery. A tantra massage aims to reconnect you with the sensitivity of your body and with your breathing; relaxation shows up, but as a side effect rather than the target. If your back is wrecked from work, the relaxing one serves you better. If what you have is the sense of living disconnected from your own body, the tantra one goes to that layer.
The relaxing massage works by area and by muscle group, with kneading, pressure and friction. The tantra one works in long continuous strokes that treat the whole body as a single piece, brings breathing in as an active part of the session, and uses rhythm — often much slower — as its main tool. It is not a gentle relaxing massage: it is a different thing.
A relaxing massage works well in fifty or sixty minutes. A tantra massage needs ninety at minimum, because much of the work is getting the nervous system to drop a gear before anything else starts. A one-hour tantra session is a half session, which is why serious practitioners do not offer them.
In a relaxing massage nobody asks how far you want to go, because there is no need. In a tantra massage that conversation is compulsory: what is included, what is not, and what limits you set. If a place offers tantra and skips that part, they are not doing tantra — they are doing something else without telling you.
You do not have to choose for good. Plenty of people alternate relaxing massage for physical upkeep with tantra for the deeper work, and it works. If you have never had either and arrive with specific physical pain, start with the relaxing one; if you arrive with your head racing and your body switched off, start with tantra.
No. It is body work with limits agreed before starting and respected throughout. The person receiving sets the pace. Places using 'tantric' as a euphemism usually give themselves away by never explaining the frame.
It depends on what is tightening you. Muscular tension, the relaxing one. Sustained mental tension, tantra usually reaches deeper because it works the breath and the nervous system, not just muscle.
Yes. No previous experience is needed. Everything is explained beforehand, it starts gently, and you can stop at any point.