Hi, striving4peace.
This is a hard question to answer. Not because it is hard, but because to answer it one need to be very open. Well, I guess this thread will get buried after all.
I'm no PUA and I'm no Carrie Bradshow, but I've known good sex before marriage. During marriage I was fair to my wife. So I can tell from two sides.
When I've met my future wife and we've started dating, it turned out she was still a virgin. Before that I've more then once was unknowingly attracted to virgins and had a few bitter disappointments. You know, in my country, when you meet a virgin who is over 16 she usually has no experience with intimate relationships. Any of it. No petting, no oral sex, even kissing is inexperienced. I have to teach them. And here is problem number one. If both partners are inexperienced, the chances that they will learn as they go are slim. This usually means little fun for the girl. The nature was kinder to the guys in this respect.
So in my early years several times we've broke up with girls and they stayed virgins. Mostly because I was not ready to take responsibility to teach them.
By the time I've met my future wife, I was ready to try. I've learned the ropes, and I was in love. This helps.
Well. That was not easy. Turns out that sexual adaptation for girls is a hell of a complex process. And it is a long one. We are talking months and years.
There are some surprising things going on. First of all, she gains weight and her body starts to change. Hips become wider, the face changes in a certain way, the voice, the way she walks and so on. I'm not fond of anorexic supermodels and I don't think that women should starve themselves to some abstract ideal of beauty. I'm just saying that she went for a couple of weeks trip after we've had sex for the first times and when she came back, I didn't recognize her at first. Most of the features I was physically attracted to (ahem) have changed beyond recognition. Physical attraction was not the only attraction I've had, I was in love so I've adjusted ok, but it was a nasty surprise.
Then there is a multitude of different problems below the waste. At the start of active sexual life girls start to get all sorts of infections. No STDs, just some flora and bacterias getting all excited. Sometimes it goes unnoticed, sometimes it hurts like hell and required a course of antibiotics with "no sex before it is cured" written on it. Add these little traumas, stretching and bruising, during physical adjustment down there.
Then there is an emotional level. She may cry every time you have sex. And the tears do not really look like the tears of happiness. And you have to guess if something is wrong or is it just the hormones overload. I know some girls laugh their head off during sex. I don't know if it is any better.
Speaking of hormones... At first, the only time my fiancee genuinely wanted sex is right before her period. That was the only day when the hormone level was high enough for her to become horny. Once a month was her appetite. I was 20 and I wouldn't mind having sex three times a day. So most of the time the initiative was mine and I had to warm her up to the idea of having sex.
Now I know it were hormones. At the time I was wondering if she loves me or finds me attractive. That is the closest to sexual incompatibility I've experienced.
All above combined created a very frustrating and difficult situation for both of us. You know, there are books on sex later in marriage and it talks about routine, boredom and so on. We've had this from the get go.
So, incompatibility can happen and on many different levels. We've managed to overcome these problems. However it took all my skills of self control, all my psychology training to keep a positive outlook. Still it took us about 5 years before the situation started to improve. In fact we were not married all this time. I've just behaved as a husband supposed to behave. Not that girls take that for anything without the wedding
I guess, it could have been done faster. We could have went to therapy. I could have been more insisting to have sex just for practice sake. Many "coulds" here. I was how it was and now it is all good and will become better.
I can imagine that the average man would have either break up or have a multitude of affairs in this situation. I'm no saint, and I've thought about it more then once. But as main character of "Highway 60" once said - "thinking about it yes, doing it - no"
So, I'd say, if sex life is important for one of the partners you better try it before the wedding. It's hard to anticipate all problems.
Unfortunately from the moral point of view, the efficient strategy to learn sex is to have sex and preferably with different partners. This way you learn to tell the bad from the good, to identify when you are the problem and when the partner is and what is the problem. However, I understand that what I'm suggesting borders with being promiscuous and is not acceptable for some.
Learning from books and forums is helpful to an extent. I find that the people tend to be untruthful when writing about their sexual experience. Plus, sex is physical, it is very hard to explain it with words. I've tried to be very sincere in this post, but I'm afraid you've got a very vague idea how hard, but at the same time not hopeless can it all be.
Well, if you are sure that your love is strong enough, you can try "marriage first" approach. But be responsible and realistic that if something goes wrong, the marriage is unlikely to last. And yes, it is the man who is likely to be the bastard and quit. Please, be honest with yourself and don't hold it just against him.