Great question. The answer is one that only you can determine, but I'll throw out a few comments.
The launching situation, where we are, isn't too bad. Usually, I launch during the week and have the ramp almost to my self. Fowl river, river shack, Macnally Park are all pretty good spots. Navco Park is probably ok, but it's a long run to the bay. Dauphin Island has some nice looking spots that I haven't tried yet - but hope to. You might run into the odd issue now and then, but it won't be the norm. Having said that, holiday weekends will probably be hectic.
Keeping a boat in a slip will likely result in your using the boat more often. But, a slip is an additional cost each month - and not insignificant. How will you feel about the boat during squalls, hurricanes, etc? If you can insure it and just take the loss without too much angst, then it probably won't keep you up at night. If, however, you have the tendency to worry about your stuff to the point of running down to the marina at 2am to check your lines in a blow; you may be a trailer sailer. Our mutual keel boat buddy doesn't seem to be too worried about his boat in its slip. Of course he's been through losing one in a hurricane before, and came out ok in the insurance settlement.
Think Day sailing initially. How many "family" members will you be taking on a typical sailing trip. 26M cockpit is comfortable at 4, and starts getting pretty tight at 6. We had six before the grand twins, and could easily enjoy a day sail on my 26M. But, we're a tight bunch. You won't be using overnight accommodations in the summer in Mobile unless you add AC and stay in a marina (or take a generator). But, again, 4 is ok, more starts to get a bit tight. If your family is close, 6 is doable. Also, what is the level of comfort expectation? My brother's wife will go primitive camping. My wife's idea of camping is the Hampton Inn. No AC, no hot shower with infinite water, are tough sells. My overnights will be restricted to fall and spring (possibly mild days in winter).
Bigger boat at a lower initial price is hard to argue. If you can't store your trailer boat at your house in covered storage, and would have to pay for storage somewhere, that's a factor as well.
If you are a member of a yacht club, you may be able to get a good rate on a slip, but you'll have to shop around to see what the rates are for the boat length you're looking at. You'll want to check if they have pumpout facilities if you have a marine head, power, and water.
A Mac power sailer isn't the only enjoyable way to go boating. It suits my current needs perfectly, but I'm an odd guy.
Either way you decide, you can't lose. You'll be on the water in a boat.
M26 for some time now. Well I have narrowed my search to two M26's. Now after doing much research I am dealing with a fudundrum. Where will I keep it? I was reading a thread on here from a guy who was having nightmares launching his 26 at public boat ramps. There were responses to him from other owners saying that they fixed this issue by acquiring a wet slip to keep their boat. 
that I've kept in a slip for 13 years. I have never trailored it to any other launch site (only partly because I've never had a vehicle that can tow it).
