Summoning a demon is not a good idea for a beginner, neither is casting a spell. I would suggest researching and learning about magick and how it works.
If you want with the spell to just draw the person for sex, I'd go for the Succubus. A Succubus also won't offer you true love, she will just come for sex, they are lustfull entities.
I second Freya's comment. Learning about magick first is crucial in helping to secure a safe spell casting and a more efficient spell cast. Also, summoning a powerful entity is not the thing a beginner should do. Once you understand the basis of magick I would suggest doing something like sigil craft which is a very safe and educational way to start on a magickal path in my opinion.
If you question starts with asking if you should summom something, would it be better to summon something or how do you summom something, the answer is no. If you have to ask, you are not ready.
Likewise, if you are trying to force a person to love you, the answer would be no. A spell to draw love to you, yes. Trying to force a specific person to a specific behavior, no. At best it woud only be superficial and ultimately would not last.
If you are a beginner, your time would best be served learning about magic, learning and practicing the basics and truly becoming good at it. In the process you will learn what can be done and when it is appropriate to do so, in accordance with what ever tradition you chose to follow.
Because Succubi are lustfull it doesn't mean they all have bad intentions of hurting and tricking you. There are many sub-categories of them also. Why some not be friendly?
Succubi operate in the emotional spectrum, as primarily yin-based creatures though with a full range, and working with sexual energy.
To say that a succubus is incapable of love is akin to say that a prostitute is incapable of love. Sure people make a connection between lust and love, even though they are not the same thing by any stretch of the imagination, but they are also not unconnected and not mutually exclusive.
As an answer to the OP, it definitely depends on what you want and how you plan to act with and on it, as well as how skilled you are.
Neither of those things are "easy", countless things can go wrong, if there is a result to begin with. A succubus can become a major problem, that you can't get rid of. A love spell may lead to a rape. And so on.
Meditate, or divine, preferably both, upon it, and your answer will be laid out before you.
