I went from a Compadre and a Vaquero to an F2 just because I wanted a decent take on vacation detector that was fast...I slipped into a screen unit just in case I lent it out because I thought it would be easier for a newbie.
I found that I really bonded with that F2 way more than I thought possible, I had a ton of fun using and learning it, found so much from the first hunt and for the next 3 years it became my prime hunting tool.
Even though it was a simple unit with just a few adjustments I learned there was way more to its language and behavior than I ever thought possible and because I learned to understand it so well I was wildly successful.
Gold, silver, old coins, tons of clad and so much more made it into my collection and it paid for itself more than 10x's over in those 3 years...the fun I had using it was incalculable.
The threads I wrote about what I learned and the pictures of my finds in those posts and threads ended up selling many F2's to some extremely happy new owners, I helped all that asked about how they could also get the best out of this deceptively simple tool and at least 4 members of my club that owned much more advanced detectors bought them too because I kept winning contests month after month, most coins, best jewelry, most unusual and much more.
One told me it seemed like it was a magic detector but I replied it wasn't magic at all, the magic was in how well I learned it to such a deep level and how easily I could understand it after I did.
I wondered if I could do this well with an entry level unit what could I do with a more advanced and powerful tool so I aimed for a new F75....but a fire sale price of $400 on a brand new F70 passed my way so I jumped on that and never looked back.
It was incredible, I knew the Fisher language well but there was so much more to learn with this one and all that massive power and extra settings helped to bring my game to a whole new level in quality of finds and the depths and challenging sites and conditions I could find them in.
That unit paid for itself in the first few months I swung it in the clad, older coins and silver and gold jewelry it found and it only got better after that when I learned it to much deeper levels.
I came to find out I preferred swinging the F70 to using the F75, the way it felt and balanced in my hands and the way the controls worked suited me and my style of hunting better but that was just a personal thing...I am pretty sure if I would have chosen the F75 instead I would have learned to love that one just as much but that was not my fate at the time.
Back then, (2014), the F70 with the 11" DD coil was over $700 new and the F75 was at $1000 or more but the landscape has changed immensely in the last couple of years.
All kinds of great detectors have come into the market at the entry, midrange and higher levels and the prices have dropped to insane levels.
The F70 with that big coil now sells for $400 in its new form as the Teknetics Patriot and compared to the same $400 price that the F4 used to be the difference is also unbelievably insane.
Way more power and abilities in that Patriot, the difference is incredible, also the flagship F75 with a crazy amount of programs and extra settings has been dropped down to the $500-$600 level.
I chose to stay in the Fisher line because I spent so much time learning that language and that seemed logical to me, it turns out everything I learned and knew transferred over to my upgraded F70 easily but as I mentioned there was just a whole lot more there to learn if I chose to do that...and I did and 4 years later I am still happily learning.
My F2 could not find targets at the 10-15" depth level in good soil but my F70 could.
My F2 in extreme iron infested sites struggled, the F70 with the right settings conquered them easily.
In the mineralized dirt I hunt in now the F2 was throttled as is most detectors around here but the F70 excelled here too with the right settings which surprised, shocked and pleased me to no end and still does.
I can't tell you what to do or what detector to move to or even if you should change brands, all I can tell you is my story, my progression and what worked in my career.
The choices I made were the right path...for me, as a satisfied Fisher owner it might be the same for you with 3 years experience standing behind that F4.
Greater power and depth should be there in most any upgrade you decide on, your job is to figure out what extra settings, programs and/or features you think might be helpful to you to get you to the next level and how much you want to spend to get there.
For me the F70/Patriot did it all and then some, hopefully your decision will be easy as mine was and just as rewarding.
Good Luck!