Both monohulls and multihulls in that size range are capable of bluewater passages, as well as for use as a coastal cruiser. One good book to read regarding small sailboats, that are fairly capable, is "Twenty Small Sailboats to Take You Anywhere," which you can find at http://tinyurl.com/ruzrc
Some boats that I would recommend in that size range would be:
: Contessa 26 (a very solid little boat, as made famous by Tania Aebi)
, Alberg 30, Pearson Triton 28, Albin Vega 27, Catalina 27, Bristol 27. I've sailed on all of these but the Contessa.
: Corsair F28, Telstar 28 (both of these are trimarans
) Heavenly Twins 27 Catamaran I've sailed on the two trimarans quite a bit, but not the cat.
You do not say what your budget is, and these boats will vary quite a bit in price. The monohulls I've mentioned are only availble used, and the two trimarans are available both new and used (although the Telstar is fairly new and not many will be available used), while the Heavenly Twins cat is only available used.
A good book to read about the differences between multihulls and monohulls is Chris White's "The Cruising Multihull"
, which you can find at http://tinyurl.com/ro66j
Although Chris's book is a bit on the older side, the discussions in it are still quite valid, and he makes his points without getting into the quasi-religious monohull vs. multihull fanatic mindset.
The two trimarans have the ability to fold and will have reasonable marina costs compared to the catamaran. They are also both easily trailerable, and can be stored out of the water, on their trailers in the off season, which may reduce your storage costs. All of the monohulls are boats that will pretty much stay in the water, and can not be trailered in any reasonable way.
Monohull or Multihull:
One argument that many try to make is that multihulls do not sail well. This is no longer true, as most modern trimarans sail quite well and point at least as well as monohulls. The cruising catamarans can have some problems pointing as well or sailing as well as monohulls, as they do not have a center hull to pivot around and they tend to have a bit more windage than the trimarans or monohulls. Another argument that monohull sailors will try to make is that multihulls are not self-righting. Chris White's argument, and this is one I agree with, is that most multihulls are far more resistant to sinking, than are monohulls... would you rather be on a multihull that is capsized, or a monohull that is sitting upright on the bottom of the ocean.
It is a personal choice. A properly sailed multihull is not very likely to capsize. Generally, the majority of non-sport multihulls that capsize, are due to the operator not sailing it properly...
A couple of major differences in the way the two types of boats sail is in heavy weather. On a monohull, you will reef for the lulls, and on a multihull, you will tend to reef for the gusts... Modern multihulls are also far more unlikely to broach in bad weather. This is not to say they will not broach if sailed badly, as any boat can be forced to broach, but if sailed properly, they're much less likely to do so.
Sailing on a multihull, and cruising on one, is often far more comfortable than on a monohull... as they heel significantly less than most monohulls. Most multihulls have far shallower drafts than similarily sized monohulls, and this allows you to explore more areas, and in bad weather, gives you more choices of refuge. Trimarans will generally have less living space than similarly length monohulls, as most only use the main hull for accommodations, and do not generally have a bridge deck of any size, and the main hull is usually far narrower than a monohull of the same length. Catamarans, will tend to have more space than a similar length monohull, but often at the cost of sailing performance. Monohulls are far less sensitive to weight and loading than most multihulls. Multihulls, especially the large catamarans, give you a lot of space, but do not perform well, should you choose to fill all that space up.
You might find my blog useful, as it describes the reasons for making the choice between various boats, including several monohulls and the two trimarans above: http://tinyurl.com/zs8q2
I hope this helps. If you have any more questions, you can PM me.