Faster charging rates actually do more harm to batteries than slower chargers. Every deep discharge takes life out of a battery.
I would recommend a 20 Amp or even less for a small charger which keeeos thevweight down also. You should calculate how long it takes to charge your bank. What you need to decide is how long you want to wait for an 80% charge. The last 20% will be slower.
40 Amp Chargers are impressive and useful f you need to top off your batteries in a few hours.
I have the 20 Amp 3 stage charger in my boat serving 2 4D batteries. All modern chargers are 3 stage chargers--which is mandatory for a trailer or a boat. Mine has an echo charger for my boat's starter battery which, I'd actually prefer to have its own charger.
Prior to this I had a 58 pound 60 Amp charger/3000 watt inverter--which gave me nothing but trouble. I don't see much point in having an inverter that draws that much power. I'd rather have 3 small ones that waste less power. The only purpose I can see for an inverter that big is to run a microwave
briefly and with the motor running, to ease the burden on he batteries.
If you keep your battery topped off it will last 7-8 years. A trickle charger or solar panel
fits that need well.
Even a cheap little motorcycle battery charger, kept plugged in all the time when the trailer is not in use will save a battery.
Consider that if your battery freezes it is ruined and that if kept topped up it can't freeze.
So in summary. I am a fan of cheap slow chargers, and using them all the time.