The seated cajon with a bass port on the front is usually called a “bass cajon” – in my experience, there are two differences from a regular cajon.
1. They generally have a much bigger and more boomy bass note than cajons with the pass port on the back. The difference is not just the location of the bass port, but also the bass ports are longer, which causes the bass notes to sustain for longer.
2. The bass part of the sound is projected forward. If you’re jamming with other musicians, they will hear the sound directly, rather than hearing the echo from the well behind you.
It comes down to taste and preference, I think – personally, I love the big boomy sound of the bass cajon.
I have one of these myself:
This a cheap cajon and it was my first. It’s fine as a starter cajon, I think – but it’s not the best build quality, and I’ve already had to repair and improve it twice. I will probably replace this with a brand name bass cajon at some point.
Note that the bass sound is extremely boomy on this one – you may find it’s too much if you’re going to jam with someone.
I also have this “slap top” cajon with a front bass port:
This is my absolute favorite instrument – it’s more portable than a seated cajon, more comfortable to play for me personally, and the bass sound is surprisingly good for such a small instrument. I find it’s incredibly versatile – it has a whole palette of different sounds. (I count 7 distinct sounds at this point!)
If you decide to try a slap top, I highly recommend getting a seated cajon as well – I mostly play the slap top when I’m just playing around, but I practice every groove and fill on the seated cajon as well, because (A) that’s how to the course teaches them, and (B) I’m hoping this trains my brain to cope with different physical layouts of different percussion instruments in the future.
Cheers and have fun. 🙂