There are two types of trainer pants - reusable or disposable.
With the reusable ones your child will feel 'wet' and with the disposable there's usually a picture that fades away (or the opposite, appears) if the nappy gets wet.
The theory is that when a child wets himself/herself, they are suppose to feel the wetness and tell you, and learn from the experience.
For some children this does work. For others, like my dd, it doesn't. With the reusable version, my dd merely told me when she needed changing. She wet them again and again because she didn't understand that she was suppose to take them off and use the potty/toilet. Far easier just to wee and poo in the reusable trainer pants and let mum clear things up.
The disposable ones didn't necessarily feel wet and quite frankly, dd didn't care if the picture appeared/disappeared. Again, far easier to wee and poo in the disposable trainer pants and let mum clean up.
In my opinion, disposable trainer pants are just expensive pull ups. Again, in my opinion, you are far better off just putting your daughter in ordinary knickers/pants. After the first week of toilet training, my dd would genuinely get upset if she had wet herself and she certainly did learn that when she did a wee in her knickers, the wee went everywhere. It wasn't soaked up conveniently by the trainer pants to that she could continue what she was doing.
I used the pull ups when we went out because I didn't want to embarrass my dd in public. There's nothing worse than needing a wee, not being able to get to the toilet in time, and getting soaking wet in front of everyone. Not all people are considerate and yes, I should ignore them but I prefer to avoid the whole situation in the first place.
The same thing for night time. I don't particularly want to have to wake up at night to the sound of a crying 2 year old, who has a wet bed that needs changing, and night clothes too, and for hygiene reasons, probably needs a bath/wash. My dd was only dry at night just after 2 years and 10 months.
To answer your question: If money is no problem and you?re not that bothered about environmental impacts, disposable trainer pants are great. They are light, non bulky and easy for a child to pull up and down ? certainly easier and less bulky than the branded Pull-Ups.
If you are environmentally aware, reusable is a good option, especially in a dry summer. Our summers here up in the North of England always seem to be wet and I therefore end up using the tumble dryer which totally defeats the environmental cause. Tumble Driers must be one of the least environmentally friendly appliances.
Pull-ups, in my opinion, are the best option, especially if you are only going to use them at night time and when going out. Disposable but cheaper than disposable trainer pants. The only drawback is that dd found them quite difficult to pull up and down but we solved this by going up a size, that is using the 15kg+ ones despite dd only weighing 12kg.