if it's your first and you don't know much about them then you need to learn the basics and what they do first.
we all have opinions and those are based on what we have used or want to use if it's outside our budget like say a marcum RT9 is for many. the story of you get what you pay for holds true on sonars also.
my advice besides learning what they offer is try to imagine you using it and how and where you;ll be using it at. a dual view/cone transducer gives you the most versatility by focusing the beam to a a narrow beam when needed like in weed beds or deeper water, while the wide cone gives a bigger area of what it can see at any given time.
then you have to think of what type to buy. do you think a mechanical flasher will keep you satisfied and if so for how long. if you buy a beginners model and then want more from it, you'll have to upgrade and buy again. this gets to be expensive, so maybe buy the most expensive you can afford to start with and learn how to use it and the extra features it may have came with like they do with digital units.
i learned the hard way that this happens.
digital units offer the maximum user interface by allowing you to adjust it to your liking and be preprogrammed or a what you see is what you get like mechanical flashers are. some digital units like the marcum lx6/7/9 have a choice of you using up to 4 charts out of a variety of 6 to pick from and the back ground color. these also allow users to upgrade the software they use to include tweaks and new features. it doesn't happen often, but it is a nice option.
right now, i would always suggest looking into digital ice sonar only.
(if you can't handle tech or high tech or if you want a tiny learning curve, then go with the mechanical flasher.)
so take a look at marcum and garmin is my advice. i have bad customer experience with humminbird and their repair service is over the top expensive so i suggest to avoid them because of those major problems.
garmin just came out with a expensive (1700$) sonar that has two transducers and can see sideways and show you where the fish are by scanning the entire water column in one direction only. so you have to swing it in a circle for it to see 360 degrees. i think many of us would like to own one of these. i am not sure how well it does once you use the other (vertical) transducer as far as interference and how well the sonar engine performs.
sonar engines are key to what ever you buy. so far the marcum sonar engine is the best from the units i have used. i have used vexilar and humminbirds top of the line mechanical unit and marcums lx7 and upgraded that into the lx9 for another 500$. they offer this as a service and this adds a camera to the lx7. this is great so you don't have to use two displays to try to watch fish on a camera and fish on sonar at the same time. you can use it for just one thing also. either just camera or just sonar. i often leave the camera because it is limited to what information it can give compared to a sonar.
and i have used the marcum showdown. the showdown gets muddy (it is gray scale and not color display) when plankton come it and you can't see your jig any more while the lx7/9 doesn't show them for about 90 minutes after the showdown is done for and then you can tune the lx6/7/9 to allow you to still see your jig while fishing in with the plankton. this is how you know how well the sonar engine works as far as plankton is concerned.
some people buy a digital unit and find it is too much work for them to use it and go out and buy a simple simon mechanical flasher because they changed their minds about how to use it before buying it as far as controls go. mechanical flashers use a motor to spin a platter that has colors on it so you stare at this often times loud spinning platter that makes you dizzy like they do to a friend of mine. most of those can't be turned down to use in the dark and then way too bright. digital units are backlit so you can adjust the light source.
i would avoid units built for open water and then offer an ice package for it. those are best for open water. marcum is designed for ice and then they offer an open water transducer kit. these are best for ice.
so new comments like some of us are giving you are nice, so you can hear the pros and cons after many of us have had more time to use either someone else's or our own electronics and to convey the newest of the tech.
the latest offering for battery source in a complete package is from marcum with their lithium shuttle that has a battery indicator and forward facing light and adjustable handle both up and down and swings front to back and holds a float system under the handle and has a run time of up 40 hours. one of the best options for users is to get rid of the float and use the arm that holds the transducer so it just barley is in the water. this makes landing fish so much easier and tangle free. i just bought one and i am set (for now lol). it also has a jack that can be used to power other 12 volt appliances like LED string lights or what have you. it also has two front usb charge ports and has two spots to attach ram mounts on either side and has rod holders in the back. if you buy a marcum unit, buy it with this new shuttle to get 100$ off. otherwise it is 250$. sign up on marcums webpage to get 10% off your order.
so read thru the posts and try to figure out the bad and the good and what you think will work for you. also, check out you tube for even more inside information on them. this place had a poll to clear the air about brands. it came down to two. marcum takes it tho by 42%. they are the ONLY sonar manufacturer to sponsor here!
http://www.iceshanty.com/ice_fishing/index.php?topic=331371.0if you do end up wanting a better unit, after buying your first, some of us use our old unit(s) for back up or to share. like when i take my wife we each have one to use. some of us sell them and some are sold right here in the for sale section. craigs list and ebay are other ways to buy used if your on a tight budget.
