Due to having arthritis in my fingers I have had to drop poundage conisiderably over the last couple of years.  So, I am limited in the poundage that I can shoot, before anyone says "Shoot the heaviest bow you can".

Assuming an arrow weighing at least 500 grains, sharp two blade broadhead and tuned well, is there going to be a noticeable difference in pentration between a recurve and a longbow that is 45@28?

Most recurves will shoot faster than most longbows.  Many R/D longbows are blurring that distiction though.  The fastest bow will give the best penetration shooting the same arrow.  Most R/D longbows will be quieter though.

If you could live with the arching trajectory, a 600 grain arrow will give both a considerable more amount of penetration.

That's what I was thinking.  I was trying to get more input to help ease my mind.  I prefer longbows and currently own three.  The two that I am looking at hunting with are a Hornes Brushbow and a Montana Whip Classic.

Thumb ring?  Wrist release?  If just your fingers are all that has problems.  My son shoots a release with his recurve and with very little practice is quite good.  I believe most would be amazed how much of their inaccuracy is because of a bad release without knowing it.

I've thought about that but haven't been able to make myself try one yet.  It also affects the elbow on my drawing arm.

Most recurves are faster than longbows with light arrows.  Typically a longbow will start gaining ground with heavier arrows.  Say a recurve shoots 9 grains per pound 200 fps and the longbow shoots 190.  Typically if you go to 12 grains per pound they will both shoot say 175.  These numbers are just illustrations.  Longbows tend to like heavy arrows better than recurves.  Your mileage may vary.  That is my expeiriance and could be wrong in some cases.

Another way of looking at it is that most recvurves will shoot about 3-5# heavier/faster than a longbow.  I.e., a 45# recurve will shoot like a 50# longbow.  Just a generalization, of course.  Depends a lot on the particular bow designs, and as Apex has noted, severe R/D bows are blurring that distinction.

Also with joint issues I would think you would want to reduce as much irritation as possible.  Others here have had to go away from the longbow because of their tendency to be more uncomfortable to shoot.

Personally I would shoot the bow you like shooting the best.Use sharp broadheads and get your arrows flying well and everything else will take care of itself.    Shooting through something with either bow is enough and you can't tell when you are skinning one out if the arrow was sticking in the ground 4 inches or six inches after it shot through anyway.Shooting 45lbs a selfbow will kill most things. jmo

Arrows are pretty dumb.  They don't know (or care) what they are shot out of.

Just shoot the type that you like....Make sure you have a sharp broadhead and an arrow that flys tru....
   Take this set up out and go a Huntin....
I herd that one Old timer mentioned that there aint no vitals outside of those far side ribs....

You will find the Hornes delivering the same arrow with a lot more authority than the Montana.
The new R/D bows from 'boutique' bowyers are second to none; lots are sponsors on this site.

I know that both of the bows that I have shoot pretty hard for the poundage, just trying to convince myself.  I don't want to wound anything.

What Apex Predzator said.  I have a Thunderstick MOAB that is 5# less than my Big River recurve and shoots the same arrows 10 f.p.s. faster and quieter.

As long as you are around 9 to 10 grains of arrow per pound of bow weight, you will be fine with either.

Crash:
I have a very good friend whose wife took 17 animals with 17 arrows in Africa with a 42# Texas recurve. I would not really worry about which bow to use, just make sure the arrows shoot well (spin on their axis quickly) and keep the weight up.
Bob

As others are saying-good flight trumps everything else. Differences between bow styles are easily generalized as "recurves are faster with same weight arrows" but there are a gazillion exceptions and the generalization that the differences shrink as arrow weight goes up is also accurate. I offer another generalization from my own observations...The 20 inch rule. Differing bow weights, differing arrow weights, different 2 blade heads,different arhers......when it is all said and done I've noticed that an awful lot of shots penetrate 18-20 inches  no matter what game animal is shot through the ribs. 40 lb selfbow or 55 pound recurve- penetration can be surprisingly similar and almost universally adequate.