I downloaded a custom world from MTS that has a few Small Market lots. Is it possible to change other lots to this from Edit Town?

Do you want to change other lots to Community-Small Market? If that's what you want to do, you may need to install NRaas Traveler to get the Small Market option. I've had that mod for so long I can't remember if Small Market is available without it being installed.

Apologies if that's not what you meant. The Traveler mod can be found here http://nraas.wikispaces.com/ (scroll down, the mods are listed in the left column).

Yes, you will either need Traveler or create a small empty Market lot in a WA destination and import this into your homeworld. The Market lot type should be available from Edit Town in either France, China or Egypt. You might need to activate testingcheats first and the "enablelotlocking on" cheat.

It is very much different, in fact: The attraction score for Markets is one of the highest, meaning it will attract more Sims than Visitors Allowed; it's 200, while a Hangout is rated at 50 as a comparison. The Java Hut lot scores at 150. So if you want an attractive lot without closing times a Market is a nice option. The disadvantage of the Market is that it is not Late Night mixology bar enabled, i.e. no other drinks but the Spline Reticulator.
Besides, it's an option for specific gameplay. Setting the Street Market lot from the Store as a market, for example, may not give any special advantages but it simply is nicer to know that the market IS a market.

Small Market has the same value as the Java Hut: 150, although the Java place is rated higher at 175 in city worlds like Bridgeport. ITF Cafeteria is at 100. No Visitors Allowed should be 10, Hangout is 50 (60 in cities), bars are 40 (60), lounges are 50 (60), clubs are 50 (60). The Showtime Coffeehouse lot type has the highest rating in the game with 300 (450) in cities. There are, of course, other factors that determine visitor frequency, like trait modifiers, amount of community lots, hardware specs. But we are derailing the thread

Edit: Sorry, made a mistake. No Visitors is, of course, 0. Visitors Allowed is 10.

I guess it's because of the Hot Spot system, which picks three random venues on a daily basis and increases their attraction score for one day.

I didn't see this until now, does there exist an excel spreadsheet or something on this? Nice to know when I need to know it and not right now

It's in venues.xml. The list is so damn long.

That's in game files? Not a spreadsheet then, much easier with spreadsheets.

Oh, sorry...! When you said excel spreadsheets, I immediately thought of the XML file because XML and spreadsheets are related lol.

Anyway, here I've shared the venues.xml in an excel spreadsheet form. I suppose you can figure out what the table means by reading it? Otherwise you can just ask here. By the way, the table is currently being filtered. Each venue has hourly details that advertise how many Sims are preferably in a venue at a certain hour. This is what makes the table very long, so I had it filtered. If you also want to see those details, open the spreadsheet, click on the dropdown button on "Venue" column / column A, and tick the (Select All). If you want to hide the details, just untick the (blank) at the bottom of the dropdown options.

Gorgeous! I made it Apache OpenOffice, still looks right. Very useful later on thanks.

Thank you for sharing that spreadsheet. The numbers generally do look in line with game experience. However, in my games, I find the resorts to be quite popular, yet they're rated only 30 in attraction, half that of the generally dismally filled lounges which are rated at 60. Makes me wonder what else goes into computing the overall attractiveness of a lot, and whether amenities of the lot also come into play.

Yes, different lots attracts different kind of people or sims if you like. If it's a gym I guess you could have limited number of athletic sims in the hood, and therefore less sims than expected. I don't know what kind of sims go to the resort, and how many of those in your hood.

First of all it could be the resort towers. Rabbitholes seem to have their own gravitational force. You can easily see this by placing several visitor enabled rabbitholes on a No Visitors Allowed lot. The lot's intensity is 0 but the lot will be heavily populated because of the rh buildings.
And for resorts in particular my guess is that there's an additional system in place that sends random numbers of locals on "vacation" there, regardless of a resort lot's lot score, because from my experience they spend the whole day or even more there, which is unusual for an ordinary community lot, and are apparently actively pushed to stuff their faces at the buffet tables. I vaguely remember to have seen a special "BeInResort" situation or hidden buff in several tuning files, too.

And with regard to lounges, from my experience the presence of a bouncer rope, even if it is set to allow everyone in, seems to repel potential visitors right from the start.
So yes, the venue intensity scores are just a fraction of all the factors that determine visitor frequency. I, for example, have effectively ruined Bridgeport's nightlife by placing a regular Bistro rabbithole next to the grocer. I have an average of 10-15 people on that lot now and they stay for extended periods of time. Try to achieve that with a Late Night bar. The lot is set to No Visitors Allowed, btw.

Do you own the resort? IIRC, resorts tend to get more attractive when it's owned by the played household. I can't confirm this though, since my resort is bugged. No one ever comes to any resorts in my game, owned or not. Worse, in unowned resorts, no one even mans the receptionist desk. I have never been able check in the resort even once!

Yes, I do own the resort. For a town of ~100 residents, on a weekday, I'll typically have 2 to 3 residents hanging around. Weekends more. If my sims want to socialize, it's one of my go to spots to find the masses to hang out with. That's why I was surprised to see the "attraction score" set relatively low, especially in comparison to other lot types. And my front desk, bars, and whatnot stay staffed, so I'm not sure what's up with your front desk never being manned.