Re: Planning to purchase higher end shotgun. 12 ga or 20 ga?
A buddy of mine likes his 20 ga slug gun more than his 12, both Savage. Yes, more ammo choices with the 12. A shotgun slug is still a mid-range tool at that. I only like 'high percentage' shots, saving any 'hail mary's' for church. There are those that do the longer range practice, range find, & do 175 yrds or so. It would take practice & a few other things to reliably handle 200 yrds under field conditions.
I do the IL thing on a buddies lease, no center-fire allowed. I do take my 12 ga Browning Gold for back up, but my gun of choice is a Knight muzzle-loader(Elite). Yes, just a bit more fiddling to keep it running, but it really stacks em up.
Just to add, most slug guns have a 22 or so inch barrel, plenty of length & still maneuverable. Depending of what you already have or need, you could get a gun & just get the extra slug barrel. A Browning Gold would offer that option. If you get a 20 ga, just mail order your preferred slugs & take a supply with you. Even in more open conditions you can stack the odds in your favor for a closer shot. This may be by sitting on an edge towards the likely corner the deer like. Also, that 250 yrd deer mare become a 75 yrd deer if you give it some time, wind direction taken into account.
For most larger game hunting that 2nd or 3rd shot is over rated. That's why a Browning A-Bolt slug gun would be a great choice. JMHO of course.